DPP-4 inhibitors for the treatment of type 2 diabetes: a methodology overview of systematic reviews.

AIMS: To evaluate the methodological quality of systematic reviews (SRs), and summarize evidence of important outcomes from dipeptidyl peptidase-4 inhibitors (DPP4-I) in treating type 2 diabetes mellitus (T2DM). METHODS: We included SRs of DPP4-I for the treatment of T2DM until January, 2018 by searching the Cochrane Library, PubMed, EMBASE and three Chinese databases. We evaluated the methodological qualities with the AMSTAR (Assessing the Methodological Quality of Systematic Reviews) tool and the GRADE (The Grading of Recommendations Assessment, Development and Evaluation) approach. RESULTS: Sixty-three SRs (a total of 2,603,140 participants) receiving DPP4-I for the treatment of T2DM were included. The results of AMSTAR showed that the lowest quality was "a list of studies (included and excluded) item" with only one (1.6%) study provided, followed by the "providing a priori design" item with only four (6.3%) studies conforming to this item, the next were "the status of publication (gray literature) used as an inclusion criterion item", with only 18 (28.9%) studies conforming to these items. Only seven (11.1%) studies scored more than nine points in AMSTAR, indicating high methodological quality. For GRADE, of the 128 outcomes, high quality evidence was provided in only 28 (21.9%), moderate in 70 (54.7%), low in 27 (21.1%), and very low in three (2.3%). CONCLUSIONS: The methodological quality of SRs of DPP4-I for type 2 diabetes mellitus is not high and there are common areas for improvement. Furthermore, the quality of evidence level is moderate and more high quality evidence is needed.

High-bandwidth and flexible tracking control for precision motion with application to a piezo nanopositioner.

For precision motion, high-bandwidth and flexible tracking are the two important issues for significant performance improvement. Iterative learning control (ILC) is an effective feedforward control method only for systems that operate strictly repetitively. Although projection ILC can track varying references, the performance is still limited by the fixed-bandwidth Q-filter, especially for triangular waves tracking commonly used in a piezo nanopositioner. In this paper, a wavelet transform-based linear time-varying (LTV) Q-filter design for projection ILC is proposed to compensate high-frequency errors and improve the ability to tracking varying references simultaneously. The LVT Q-filter is designed based on the modulus maximum of wavelet detail coefficients calculated by wavelet transform to determine the high-frequency locations of each iteration with the advantages of avoiding cross-terms and segmenting manually. The proposed approach was verified on a piezo nanopositioner. Experimental results indicate that the proposed approach can locate the high-frequency regions accurately and achieve the best performance under varying references compared with traditional frequency-domain and projection ILC with a fixed-bandwidth Q-filter, which validates that through implementing the LTV filter on projection ILC, high-bandwidth and flexible tracking can be achieved simultaneously by the proposed approach.

RhoA/ROCK signaling and pleiotropic α1A-adrenergic receptor regulation of cardiac contractility.

AIMS: To determine the mechanisms by which the α1A-adrenergic receptor (AR) regulates cardiac contractility. BACKGROUND: We reported previously that transgenic mice with cardiac-restricted α1A-AR overexpression (α1A-TG) exhibit enhanced contractility but not hypertrophy, despite evidence implicating this Gαq/11-coupled receptor in hypertrophy. METHODS: Contractility, calcium (Ca(2+)) kinetics and sensitivity, and contractile proteins were examined in cardiomyocytes, isolated hearts and skinned fibers from α1A-TG mice (170-fold overexpression) and their non-TG littermates (NTL) before and after α1A-AR agonist stimulation and blockade, angiotensin II (AngII), and Rho kinase (ROCK) inhibition. RESULTS: Hypercontractility without hypertrophy with α1A-AR overexpression is shown to result from increased intracellular Ca(2+) release in response to agonist, augmenting the systolic amplitude of the intracellular Ca(2+) concentration [Ca(2+)]i transient without changing resting [Ca(2+)]i. In the absence of agonist, however, α1A-AR overexpression reduced contractility despite unchanged [Ca(2+)]i. This hypocontractility is not due to heterologous desensitization: the contractile response to AngII, acting via its Gαq/11-coupled receptor, was unaltered. Rather, the hypocontractility is a pleiotropic signaling effect of the α1A-AR in the absence of agonist, inhibiting RhoA/ROCK activity, resulting in hypophosphorylation of both myosin phosphatase targeting subunit 1 (MYPT1) and cardiac myosin light chain 2 (cMLC2), reducing the Ca(2+) sensitivity of the contractile machinery: all these effects were rapidly reversed by selective α1A-AR blockade. Critically, ROCK inhibition in normal hearts of NTLs without α1A-AR overexpression caused hypophosphorylation of both MYPT1 and cMLC2, and rapidly reduced basal contractility. CONCLUSIONS: We report for the first time pleiotropic α1A-AR signaling and the physiological role of RhoA/ROCK signaling in maintaining contractility in the normal heart.

[Effects of soy isoflavones and major active component genistein on the expression of ovarian estrogen receptor-α in rats].

OBJECTIVE: To investigate the effects of soy isoflavones (SI) on the expression of estrogen receptor-α (ER-α) in senile rat ovaries and ovarian granulosa cell cultured in vitro treated with genistein, a major active component of SI. METHODS: The animal model of perimenopause rats was established by unforced aging. The animals were treated by intragastric administration (ig) with low (50 mg/kg), middle (158 mg/kg) and high (500 mg/kg) dose of SI for 8 weeks. The expressions of ER-α mRNA and protein were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry respectively. The granulosa cells of rat ovaries were isolated and administered with genistein (0, 0.1, 1, 5, 10, 100 µmol/L) for 48 h and the expression levels of ER-α mRNA detected by RT-PCR. RESULTS: The ER-α mRNA expression levels of the low, middle and high dose groups of SI (0.207 ± 0.014, 0.316 ± 0.073 and 0.402 ± 0.170 respectively) were higher than those of the model group (0.671 ± 0.170) (all P < 0.01). The expression levels of ER-α protein for the low, middle and high dose groups of SI (7.35 ± 4.90, 13.90 ± 5.12 and 23.79 ± 10.31 respectively) were higher than those of the model group (2.74 ± 0.09) (all P < 0.01). The expression levels of ER-α mRNA in granulosa cells treated with 1, 5, 10 µmol/L genistein for 48 h were 0.927 ± 0.232, 1.067 ± 0.154, 1.118 ± 0.126 respectively (all P < 0.01). They were higher than those of the control group (0.671 ± 0.170). But the expression levels of 100 µmol/L genistein group were lower than those of the control group (P < 0.05). CONCLUSION: Soy isoflavones can up-regulate the expressions of ER-α mRNA and protein in senile rat ovaries. As a major active component of soy isoflavones, genistein can regulate the expressions ER-α mRNA in granulosa cells of rat ovaries. Such an effect is concentration-dependent. And 1-10 µmol/L genistein may up-regulate the expression of ER-α mRNA.

Regulation of murine cardiac contractility by activation of α(1A)-adrenergic receptor-operated Ca(2+) entry.

AIMS: Sympathetic regulation of cardiac contractility is mediated in part by α(1)-adrenergic receptors (ARs), and the α(1A)-subtype has been implicated in the pathogenesis of cardiac hypertrophy. However, little is known about α(1A)-AR signalling pathways in ventricular myocardium. The aim of this study was to determine the signalling pathway that mediates α(1A)-AR-coupled cardiac contractility. METHODS AND RESULTS: Using a transgenic model of enhanced cardiac α(1A)-AR expression and signalling (α(1A)-H mice), we identified a receptor-coupled signalling pathway that enhances Ca(2+) entry and increases contractility. This pathway involves α(1A)-AR-activated translocation of Snapin and the transient receptor potential canonical 6 (TRPC6) channel to the plasma membrane. In ventricular cardiomyocytes from α(1A)-H and their non-transgenic littermates (or WTs), stimulation with α(1A)-AR-specific agonists resulted in increased [Ca(2+)](i), which was dose-related and proportional to the level of α(1A)-AR expression. Blockade of TRPC6 inhibited the α(1A)-AR-mediated increase in [Ca(2+)](i) and contractility. External Ca(2+) entry, underlying the [Ca(2+)](i) increase, was not due to store-operated Ca(2+) entry but to a receptor-operated mechanism of Ca(2+) entry resulting from α(1A)-AR activation. CONCLUSION: These findings indicate that Ca(2+) entry via the α(1A)-AR-Snapin-TRPC6-pathway plays an important role in physiological regulation of cardiac contractility and may be an important target for augmenting cardiac performance.

Nesprin-1 and actin contribute to nuclear and cytoskeletal defects in lamin A/C-deficient cardiomyopathy.

Lamin A/C mutations are the most common cause of familial dilated cardiomyopathy (DCM) but the pathogenetic mechanisms are incompletely understood. Nesprins are spectrin repeat-containing proteins that interact with lamin A/C and are components of the linker-of-nucleoskeleton-and-cytoskeleton (LINC) complex that connects the nuclear envelope to the actin cytoskeleton. Our aim was to determine whether changes in nesprin-1 and actin might contribute to DCM in homozygous Lmna knockout (Lmna(-/-)) mice. Here we find that Lmna(-/-) cardiomyocytes have altered nuclear envelope morphology, disorganization of nesprin-1 and heterogeneity in the distribution of nuclear and cytoskeletal actin. Functional interactions of nesprin-1 with nuclear G-actin and with the cytoskeletal γ-actin, α-cardiac actin and α-smooth muscle actin (α-SMA) isoforms were shown by immunoprecipitation and Western blotting. At 4-6 weeks of age, Lmna(-/-) mice had normal levels of γ-actin and α-cardiac actin, but α-SMA expression was increased by 50%. In contrast to the predominant vascular distribution of α-SMA in WT ventricular sections, α-SMA had a diffuse staining pattern in Lmna(-/-) sections. Osmotic swelling studies showed enhanced radial swelling in Lmna(-/-) cardiomyocytes indicative of cytoskeletal instability. The distensibility of Lmna(-/-) cardiomyocytes with osmotic stress was reduced by addition of α-SMA-specific fusion peptide. Our findings support a model in which uncoupling of the nucleus and cytoskeleton associated with disruption of the LINC complex promotes mechanical instability and defective force transmission in cardiomyocytes. Changes in the distribution and expression patterns of nuclear and cytoskeletal actin suggest that diverse transcriptional and structural defects may also contribute to DCM in Lmna(-/-) mice.

[Effects of yikunning on the expressions of bcl-2 and bax in rat ovaries during perimenopausal period].

OBJECTIVE: To investigate the effects of Yikunning (YKN, Chinese Traditional Medicine) on the expressions of bcl-2 and bax in rat ovaries during perimenopausal period. METHODS: Thirty female Wistar rats during perimenopausal period were selected by unforced aging. Then the rats were divided into 3 groups randomly: YKN group, Livial control group and Aged control group. Ten young female Wistar rats were selected as young control group. Intragastric administrations were conducted for 4 weeks once daily continuously. The expressions of Bcl-2 Bax mRNAs and proteins in rat ovaries were detected by RT-PCR and Western blot. RESULTS: The levels of Bcl-2, Bax mRNAs and proteins in rat ovaries in YKN group were higher than those in Aged control group, which showed differences among them (P < 0.01). The Bcl-2/Bax mRNA rate and protein rate in rat ovaries in YKN group were higher than those in Aged control group, which showed differences among them (P < 0.05 or P < 0.01). CONCLUSION: YKN could increase the expressions of Bcl-2, Bax mRNAs and proteins and up-regulate the Bcl-2/Bax mRNA rate, protein rate in rat ovaries during perimenopausal period, which might be one of the molecular mechanisms of YKN postponed the ovarian failure and cured perimenopausal syndrome.

Effects of mechanical stress and carvedilol in lamin A/C-deficient dilated cardiomyopathy.

RATIONALE: Mutations in the LMNA gene, which encodes the nuclear lamina proteins lamin A and lamin C, are the most common cause of familial dilated cardiomyopathy (DCM). Mechanical stress-induced apoptosis has been proposed as the mechanism underpinning DCM in lamin A/C-deficient hearts, but supporting in vivo evidence has been lacking. OBJECTIVE: Our aim was to study interventions to modify mechanical stress in heterozygous Lmna knockout (Lmna(+/-)) mice. METHODS AND RESULTS: Cardiac structure and function were evaluated before and after exercise training, thoracic aortic constriction, and carvedilol treatment. Lmna(+/-) mice develop adult-onset DCM with relatively more severe disease in males. Lmna(+/-) cardiomyocytes show altered nuclear morphology and perinuclear desmin organization, with enhanced responses to hypo-osmotic stress indicative of cytoskeletal instability. Despite these structural defects that provide a template for mechanical stress-induced damage, young Lmna(+/-) mice subjected to 6 weeks of moderate or strenuous exercise training did not show induction of apoptosis or accelerated DCM. In contrast, regular moderate exercise attenuated DCM development in male Lmna(+/-) mice. Sustained pressure overload generated by thoracic aortic constriction depressed ventricular contraction in young wild-type and Lmna(+/-) mice with no sex or genotype differences in the time-course or severity of response. Treatment of male Lmna(+/-) mice from 12 to 40 weeks with the beta-blocker, carvedilol, prevented the dilatation and contractile dysfunction that was observed in placebo-treated mice. CONCLUSIONS: These data suggest that factors other than mechanical stress-induced apoptosis contribute to DCM and provide the first demonstration that regular moderate exercise and carvedilol can modify disease progression in lamin A/C-deficient hearts.

The rise of [Na(+)] (i) during ischemia and reperfusion in the rat heart-underlying mechanisms.

Intracellular Na(+) concentration ([Na(+)](i)) rises in the heart during ischemia, and on reperfusion, there is a transient rise followed by a return toward control. These changes in [Na(+)](i) contribute to ischemic and reperfusion damage through their effects on Ca(2+) overload. Part of the rise of [Na(+)](i) during ischemia may be caused by increased activity of the cardiac Na(+)/H(+) exchanger (NHE1), activated by the ischemic rise in [H(+)](i). In support of this view, NHE1 inhibitors reduce the [Na(+)](i) rise during ischemia. Another possibility is that the rise of [Na(+)](i) during ischemia is caused by Na(+) influx through channels. We have reexamined these issues by use of two different NHE1 inhibitors, amiloride, and zoniporide, in addition to tetrodotoxin (TTX), which blocks voltage-sensitive Na(+) channels. All three drugs produced cardioprotection after ischemia, but amiloride (100 microM) and TTX (300 nM) prevented the rise in [Na(+)](i) during ischemia, whereas zoniporide (100 nM) did not. Both amiloride and zoniporide prevented the rise of [Na(+)](i) on reperfusion, whereas TTX was without effect. In an attempt to explain these differences, we measured the ability of the three drugs to block Na(+) currents. At the concentrations used, TTX reduced the transient Na(+) current (I (Na)) by 11 +/- 2% while amiloride and zoniporide were without effect. In contrast, TTX largely eliminated the persistent Na(+) current (I (Na,P)) and amiloride was equally effective, whereas zoniporide had a substantially smaller effect reducing I (Na,P) to 41 +/- 8%. These results suggest that part of the effect of NHE1 inhibitors on the [Na(+)](i) during ischemia is by blockade of I (Na,P). The fact that a low concentration of TTX eliminated the rise of [Na(+)](i) during ischemia suggests that I (Na,P) is a major source of Na(+) influx in this model of ischemia.

[Effects of soy isoflavones on the expression of Bax mRNA and Ca(2+)-ATPase activity in ovaries of perimenopause rats].

AIM: To investigate the effects of soy isoflavones (SI) on the expression of Bax mRNA and Ca(2+) -ATPase activity in ovaries of perimenopause rats. METHODS: The animal model of perimenopause rats was established by unforced aging. 12 month-old presenilins female Wistar rats were administered by intragastric (ig) with low (500 mg/kg), middle (158 mg/kg) and high (500 mg/kg) does of SI for 8 weeks. The expression of Bax mRNA in ovaries were detected by RT-PCR. Ca(2+) -ATPase activity in ovaries and MDA content and SOD activity in serum were detected by chemi-chromatometry. RESULTS: Intervention of SI could significantly decrease the expression of Bax mRNA in ovaries and MDA content in serum, increase Ca(2+) -ATPase activity in ovaries and SOD activity in serum of presenilins rats (P < 0.05 or P < 0.01). CONCLUSION: Soy isoflavones could down-regulate the expression of Bax mRNA and increase Ca(2+) -ATPase activity in aged ovaries. It is probably one of the mechanisms to improve the function of aged ovaries in perimenopause rats.

AICAR inhibits the Na+/H+ exchanger in rat hearts--possible contribution to cardioprotection.

AICAR (5-amino-1-beta-D: -ribofuranosyl-imidazole-4-carboxamide) is an adenosine analog which improves the recovery of the heart after ischemia. In some tissues AICAR enters cells and stimulates AMP-activated protein kinase (AMPK). We explored the mechanism of cardioprotection in isolated rat hearts. We confirmed that AICAR (0.5 mM) applied 10 min prior to a 30-min period of ischemia and present throughout ischemia and reperfusion caused a substantial improvement in the recovery of developed pressure on reperfusion. However, adenosine (100 microM) produced no improvement, suggesting that the mechanism of action of AICAR was not increased endogenous adenosine production. Measurements of intracellular sodium concentration ([Na(+)](i)) showed that AICAR prevented the rapid rise of [Na(+)](i), which normally occurs on reperfusion. Inhibitors of the cardiac sodium-hydrogen exchanger (NHE1) also protect the heart from ischemic damage and also prevent the rapid rise of [Na(+)](i) on reperfusion, suggesting that AICAR might cause the inhibition of NHE1. We tested this possibility on isolated rat ventricular myocytes in which the recovery of pH(i) after NH(4)Cl exposure provides a measure of NHE1 activity. AICAR (0.5 micromM) inhibited NHE1 activity in response to an acid load by about 80%. To test whether the AICAR-induced inhibition of NHE1 arose through adenosine, we used the adenosine receptor blocker 8-sulfophenyltheophylline (8-SPT) and found that it had no measureable effect. To test whether the AICAR-induced inhibition of NHE1 might occur through the activation of AMPK, we measured the activity of two isoforms of AMPK. Surprisingly, activity was reduced, whereas in many other tissues AICAR increases AMPK activity. Furthermore, this effect of AMPK was blocked by 8-SPT, suggesting that the inhibition of AMPK arose through an adenosine-receptor-related pathway. We conclude that AICAR inhibits NHE1 through an unidentified pathway. This inhibition may make a contribution to the cardioprotective effects of AICAR.

Alterations in dihydropyridine receptors in dystrophin-deficient cardiac muscle.

The deficiency of dystrophin, a critical membrane stabilizing protein, in the mdx mouse causes an elevation in intracellular calcium in myocytes. One mechanism that could elicit increases in intracellular calcium is enhanced influx via the L-type calcium channels. This study investigated the effects of the dihydropyridines BAY K 8644 and nifedipine and alterations in dihydropyridine receptors in dystrophin-deficient mdx hearts. A lower force of contraction and a reduced potency of extracellular calcium (P < 0.05) were evident in mdx left atria. The dihydropyridine agonist BAY K 8644 and antagonist nifedipine had 2.7- and 1.9-fold lower potencies in contracting left atria (P < 0.05). This corresponded with a 2.0-fold reduction in dihydropyridine receptor affinity evident from radioligand binding studies of mdx ventricular homogenates (P < 0.05). Increased ventricular dihydropyridine receptor protein was evident from both radioligand binding studies and Western blot analysis and was accompanied by increased mRNA levels (P < 0.05). Patch-clamp studies in isolated ventricular myocytes showed no change in L-type calcium current density but revealed delayed channel inactivation (P < 0.05). This study indicates that a deficiency of dystrophin leads to changes in dihydropyridine receptors and L-type calcium channel properties that may contribute to enhanced calcium influx. Increased influx is a potential mechanism for the calcium overload observed in dystrophin-deficient cardiac muscle.

The cardioprotective effects of Na+/H+ exchange inhibition and mitochondrial KATP channel activation are additive in the isolated rat heart.

The mechanisms of recovery of the isolated rat heart were studied after 30 min of global ischemia. Functional recovery was assessed by the percentage recovery of developed pressure after 30 min reperfusion and by the magnitude of the contracture on reperfusion. After a control ischemia, developed pressure recovered to only 12+/-2% of pre-ischemic control and the reperfusion contracture was very large (81+/-6 mmHg). Activation of the mitochondrial KATP channel with 100 microM diazoxide present throughout ischemia and reperfusion improved recovery of developed pressure to 36+/-3% and reduced the reperfusion contracture (53+/-4 mmHg). Inhibition of the sodium/hydrogen exchanger with 10 microM cariporide caused a larger recovery of developed pressure to 72+/-4% and further reduced the reperfusion contracture (11+/-3 mmHg). The combination of both drugs increased recovery of developed pressure to 96+/-4% and the reperfusion contracture remained small (11+/-5 mmHg). The effectiveness of the timing of exposure to these drugs was explored. When both diazoxide and cariporide were applied 2 min before the end of ischaemia and remained present during reperfusion the recovery of developed pressure was 81+/-4% and the reperfusion contracture was small (12+/-3 mmHg); neither was significantly different to the recovery when both drugs were present throughout ischemia and reperfusion. We conclude that mitochondrial damage, blocked by diazoxide, and the coupled exchanger pathway, blocked by cariporide, are two of the principal damage pathways and functional recovery appears to be complete when both are blocked. The combination of these drugs is also highly effective when given 2 min before the end of ischemia.

The role of endogenous angiotensin II in ischaemia, reperfusion and preconditioning of the isolated rat heart.

We examined the possibility that endogenous angiotensin II (AII) is involved in the regulation of the cardiac Na(+)/H(+) exchanger (NHE1) during ischaemia, reperfusion and preconditioning. Mechanical function and intracellular sodium ([Na(+)](i)) were studied in isolated, perfused rat hearts. To test whether AII production might underlie the increased activity of NHE1 on reperfusion, we applied the AII receptor antagonist losartan during ischaemia and reperfusion. Losartan significantly improved mechanical performance on reperfusion and reduced the peak [Na(+)](i) on reperfusion. It has been proposed that preconditioning inhibits the activity of NHE1 in early reperfusion. To test whether this might be because of impaired action of AII on NHE1 we applied AII throughout ischaemia and reperfusion in preconditioned hearts. AII abolished the improved mechanical recovery caused by preconditioning and the peak [Na(+)](i) on reperfusion was similar to that after ischaemia alone. Addition of the NHE1 antagonist cariporide or losartan simultaneously with AII, reversed the deleterious effects of AII on the preconditioned heart. These studies suggest that AII contributes to the activation of NHE1 in early reperfusion and that part of the beneficial effect of preconditioning may be attributed to the abolition of AII-induced activation of NHE1.

Role of the cardiac Na+/H+ exchanger during ischemia and reperfusion.

The coupled exchanger theory describes one of the central mechanisms of damage in the ischemic heart. The theory proposes that anaerobic glycolysis produces lactate and protons and that the protons can leave the cardiac cell on the cardiac Na+/H+ exchanger (NHE1). The subsequent rise in [Na+]i stimulates the cardiac Na+/Ca2+ exchanger (NCX) and results in an increase in [Ca2+]i which promotes myocardial cell damage. Although the general features of this theory are widely accepted, there is dispute about some aspects, specifically whether the NHE1 remains active during ischemia or not. We review the evidence on this issue and conclude that NHE1 is substantially inhibited during ischemia. This issue is central to the design of a clinical trial of NHE1 inhibitors in the treatment of human cardiac ischemia and the existing clinical trials are considered in this light.