Early cardiac changes in a rat model of prediabetes: brain natriuretic peptide overexpression seems to be the best marker

Effect of Blueberry Supplementation on a Diet-Induced Rat Model of Prediabetes-Focus on Hepatic Lipid Deposition, Endoplasmic Stress Response and Autophagy

Blueberries, red fruits enriched in polyphenols and fibers, are envisaged as a promising nutraceutical intervention in a plethora of metabolic diseases. Prediabetes, an intermediate state between normal glucose tolerance and type 2 diabetes, fuels the development of complications, including hepatic steatosis. In previous work, we have demonstrated that blueberry juice (BJ) supplementation benefits glycemic control and lipid profile, which was accompanied by an amelioration of hepatic mitochondrial bioenergetics. The purpose of this study is to clarify the impact of long-term BJ nutraceutical intervention on cellular mechanisms that govern hepatic lipid homeostasis, namely autophagy and endoplasmic reticulum (ER) stress, in a rat model of prediabetes. Two groups of male Wistar rats, 8-weeks old, were fed a prediabetes-inducing high-fat diet (HFD) and one group was fed a control diet (CD). From the timepoint where the prediabetic phenotype was achieved (week 16) until the end of the study (week 24), one of the HFD-fed groups was daily orally supplemented with 25 g/kg body weight (BW) of BJ (HFD + BJ). BW, caloric intake, glucose tolerance and insulin sensitivity were monitored throughout the study. The serum and hepatic lipid contents were quantified. Liver and interscapular brown and epidydimal white adipose tissue depots (iBAT and eWAT) were collected for histological analysis and to assess thermogenesis, ER stress and autophagy markers. The gut microbiota composition and the short-chain fatty acids (SCFAs) content were determined in colon fecal samples. BJ supplementation positively impacted glycemic control but was unable to prevent obesity and adiposity. BJ-treated animals presented a reduction in fecal SCFAs, increased markers of arrested iBAT thermogenesis and energy expenditure, together with an aggravation of HFD-induced lipotoxicity and hepatic steatosis, which were accompanied by the inhibition of autophagy and ER stress responses in the liver. In conclusion, despite the improvement of glucose tolerance, BJ supplementation promoted a major impact on lipid management mechanisms at liver and AT levels in prediabetic animals, which might affect disease course.

A high-sucrose diet exacerbates the left ventricular phenotype in a high fat-fed streptozotocin rat model of diabetic cardiomyopathy

Left ventricular (LV) dysfunction is an early, clinically detectable sign of cardiomyopathy in type 2 diabetes mellitus (T2DM) that precedes the development of symptomatic heart failure. Preclinical models of diabetic cardiomyopathy are essential to develop therapies that may prevent or delay the progression of heart failure. This study examined the molecular, structural, and functional cardiac phenotype of two rat models of T2DM induced by a high-fat diet (HFD) with a moderate- or high-sucrose content (containing 88.9 or 346 g/kg sucrose, respectively), plus administration of low-dose streptozotocin (STZ). At 8 wk of age, male Sprague-Dawley rats commenced a moderate- or high-sucrose HFD. Two weeks later, rats received low-dose STZ (35 mg/kg ip for 2 days) and remained on their respective diets. LV function was assessed by echocardiography 1 wk before end point. At 22 wk of age, blood and tissues were collected postmortem. Relative to chow-fed sham rats, diabetic rats on a moderate- or high-sucrose HFD displayed cardiac reactive oxygen species dysregulation, perivascular fibrosis, and impaired LV diastolic function. The diabetes-induced impact on LV adverse remodeling and diastolic dysfunction was more apparent when a high-sucrose HFD was superimposed on STZ. In conclusion, a high-sucrose HFD in combination with low-dose STZ produced a cardiac phenotype that more closely resembled T2DM-induced cardiomyopathy than STZ diabetic rats subjected to a moderate-sucrose HFD.NEW & NOTEWORTHY Left ventricular dysfunction and adverse remodeling were more pronounced in diabetic rats that received low-dose streptozotocin (STZ) and a high-sucrose high-fat diet (HFD) compared with those on a moderate-sucrose HFD in combination with STZ. Our findings highlight the importance of sucrose content in diet composition, particularly in preclinical studies of diabetic cardiomyopathy, and demonstrate that low-dose STZ combined with a high-sucrose HFD is an appropriate rodent model of cardiomyopathy in type 2 diabetes.

Puerarin-V Improve Mitochondrial Respiration and Cardiac Function in a Rat Model of Diabetic Cardiomyopathy via Inhibiting Pyroptosis Pathway through P2X7 Receptors

There is a new form of puerarin, puerarin-V, that has recently been developed, and it is unclear whether puerarin-V has a cardioprotective effect on diabetic cardiomyopathy (DCM). Here, we determined whether puerarin-V had any beneficial influence on the pathophysiology of DCM and explored its possible mechanisms. By injecting 30 mg/kg of STZ intraperitoneally, diabetes was induced in rats. After a week of stability, the rats were injected subcutaneously with ISO (5 mg/kg). We randomly assigned the rats to eight groups: (1) control; (2) model; (3) metformin; (4-6) puerarin-V at different doses; (7) puerarin (API); (8) puerarin injection. DCM rats were found to have severe cardiac insufficiency (arrythmia, decreased LVdP/dt, and increased E/A ratio). In addition, cardiac injury biomarkers (cTn-T, NT-proBNP, AST, LDH, and CK-MB), inflammatory cytokines (IL-1β, IL-18, IL-6, and TNF-α), and oxidative damage markers (MDA, SOD and GSH) were markedly increased. Treatment with puerarin-V positively adjusts these parameters mentioned above by improving cardiac function and mitochondrial respiration, suppressing myocardial inflammation, and maintaining the structural integrity of the cardiac muscle. Moreover, treatment with puerarin-V inhibits the P2X7 receptor-mediated pyroptosis pathway that was upregulated in diabetic hearts. Given these results, the current study lends credence to the idea that puerarin-V can reduce myocardial damage in DCM rats. Furthermore, it was found that the effect of puerarin-V in diabetic cardiomyopathy is better than the API, the puerarin injection, and metformin. Collectively, our research provides a new therapeutic option for the treatment of DCM in clinic.

Investigating Celastrol's Anti-DCM Targets and Mechanisms via Network Pharmacology and Experimental Validation

Methods

Data from TCMSP and GEO databases were utilized to identify targets for Celastrol on DCM. The relationship between the major targets and conventional glycolipid metabolism was obtained with Spearman correlation analysis. Experiments on animals were conducted utilizing healthy control (HC), low-dose Celastrol interventions (CL), and no intervention groups (NC), all of which had 8 SD rats in each group. To study alterations in signaling molecules, RT-PCR was performed.

Results

There were 76 common targets and 5 major targets for Celastrol-DCM. Celastrol have been found to regulate AGE-RAGE, TNF, MAPK, TOLL-like receptors, insulin resistance, and other signaling pathways, and they are closely linked to adipocytokines, fatty acid metabolism, glycolipid biosynthesis, and glycosylphosphati-dylinositol biosynthesis on DCM. These five major targets have been found to regulate these pathways. Experiments on rats indicated that P38 MAPK was considerably elevated in the cardiac tissue from rats in the CL and NC groups compared to the HC group, and the difference was statistically significant (P < 0.01). Significant differences were seen between the CL and NC groups in P38 MAPK levels, with a statistical significance level of less than 0.05.

Conclusion

Celastrol may play a role in reversing energy remodeling, anti-inflammation, and oxidative stress via modulating p38 protein expression in the MAPK pathway, which have been shown in the treatment of DCM.

Current landscape of preclinical models of diabetic cardiomyopathy

Patients with diabetes have an increased risk of developing heart failure, preceded by (often asymptomatic) cardiac abnormalities, collectively called diabetic cardiomyopathy (DC). Diabetic heart failure lacks effective treatment, remaining an urgent, unmet clinical need. Although structural and functional characteristics of the diabetic human heart are well defined, clinical studies lack the ability to pinpoint the specific mechanisms responsible for DC. Preclinical animal models represent a vital component for understanding disease aetiology, which is essential for the discovery of new targeted treatments for diabetes-induced heart failure. In this review, we describe the current landscape of preclinical DC models (genetic, pharmacologically induced, and diet-induced models), highlighting their strengths and weaknesses and alignment to features of the human disease. Finally, we provide tools, resources, and recommendations to assist future preclinical translation addressing this knowledge gap.

Impact of Dietary Fructose and High Salt Diet: Are Preclinical Studies Relevant to Asian Societies?

Fructose consumption, especially in food additives and sugar-sweetened beverages, has gained increasing attention due to its potential association with obesity and metabolic syndrome. The relationship between fructose and a high-salt diet, leading to hypertension and other deleterious cardiovascular parameters, has also become more evident, especially in preclinical studies. However, these studies have been modeled primarily on Western diets. The purpose of this review is to evaluate the dietary habits of individuals from China, Japan, and Korea, in light of the existing preclinical studies, to assess the potential relevance of existing data to East Asian societies. This review is not intended to be exhaustive, but rather to highlight the similarities and differences that should be considered in future preclinical, clinical, and epidemiologic studies regarding the impact of dietary fructose and salt on blood pressure and cardiovascular health worldwide.

SGLT2 inhibitor dapagliflozin prevents atherosclerotic and cardiac complications in experimental type 1 diabetes

Introduction

Cardiovascular disease (CVD) is two to five times more prevalent in diabetic patients and is the leading cause of death. Therefore, identification of novel therapeutic strategies that reduce the risk of CVD is a research priority. Clinical trials showed that reduction in the relative risk of heart failure by sodium-glucose cotransporter 2 inhibitors (SGLT2i) are partly beyond their glucose lowering effects, however, the molecular mechanisms are still elusive. Here we investigated the role of SGLT2i dapagliflozin (DAPA) in the prevention of diabetes-induced cardiovascular complications.

Methods

Type 1 diabetes was induced with streptozotocin (65 mg/bwkg, ip.) in adult, male Wistar rats. Following the onset of diabetes rats were treated for six weeks with DAPA (1 mg/bwkg/day, po.).

Results

DAPA decreased blood glucose levels (D: 37±2.7 vs. D+DAPA: 18±5.6 mmol/L; p<0.05) and prevented metabolic decline. Aortic intima-media thickening was mitigated by DAPA. DAPA abolished cardiac hypertrophy, and myocardial damage. Cardiac inflammation and fibrosis were also moderated after DAPA treatment.

Conclusions

These data support the preventive and protective role of SGLT2i in diabetes-associated cardiovascular disease. SGLT2i may provide novel therapeutic strategy to hinder the development of cardiovascular diseases in type 1 diabetes, thereby improve the outcomes.

The role of metabolic syndrome in sudden cardiac death risk: Recent evidence and future directions

Metabolic syndrome (MetS) is a frequent condition whose deleterious effects on the cardiovascular system are often underestimated. MetS is nowadays considered a real pandemic with an estimated prevalence of 25% in general population. Individuals with MetS are at high risk of sudden cardiac death (SCD) as this condition accounts for 50% of all cardiac deaths in such a population. Of interest, recent studies demonstrated that individuals with MetS show 70% increased risk of SCD even without previous history of coronary heart disease (CHD). However, little is known about the interplay between the two conditions. MetS is a complex disease determined by genetic predisposition, unhealthy lifestyle and ageing with deleterious effects on different organs. MetS components trigger a systemic chronic low-grade pro-inflammatory state, associated with excess of sympathetic activity, cardiac hypertrophy, arrhythmias and atherosclerosis. Thus, MetS has an important burden on the cardiovascular system as demonstrated by both preclinical and clinical evidence. The aim of this review is to summarize recent evidence concerning the association between MetS and SCD, showing possible common aetiological processes, and to indicate prospective for future studies and therapeutic targets.

Biliary cirrhosis-induced cardiac abnormality in rats: Interaction between Farnesoid-X-activated receptors and the cardiac uncoupling proteins 2 and 3

OBJECTIVES

This study aimed to evaluate the relationship between Farnesoid-X-activated receptors (FXR) as nuclear regulators of the antioxidant defense system as well as cardiac mitochondrial carrier proteins of UCP2 and UCP3 in cardiac damage induced by cirrhosis.

MATERIALS AND METHODS

Twenty-two male Wistar rats (200-250 g) were randomly divided into 3 experimental groups, including a control group (n=6), a sham-operated group (n=8), and a bile duct ligated (BDL) group (n=8). Four weeks after surgical intervention, biochemical assessment (AST, ALT, GGT, LDH, and ALP), histological observation, and molecular evaluation (FXR, UCP2, UCP3, BNP, Caspase3, and GAPDH) using real-time RT-PCR were performed.

RESULTS

Compared with the sham-operation group, the BDL group showed a significant rise in liver enzymes of AST, ALT, GGT, LDH, and ALP. Defined fibrotic and necrotic bundles and thick reticulin fibers were also found in BDL liver tissue. Besides liver morphological alterations, left ventricles of BDL ones were also associated with defined cardiomyocyte hypertrophy, myofiber vacuolization, and clear pigmentation. Findings showed a significant up-regulation of cardiac Brain Natriuretic Peptide (BNP) along with marked down-regulation in hepatic FXR, cardiac FXR, and cardiac UCP2 and UCP3. However, the expression of caspase 3 in the cardiac tissue was not affected by BDL operation during 4 weeks.

CONCLUSION

Expression of FXR as an upstream regulator of cellular redox status, besides the non-enzymatic ROS buffering defense system of cardiac UCPs, has a pivotal role in the pathogenesis of cirrhotic-induced cardiac abnormality in rats.

Fructose plus High-Salt Diet in Early Life Results in Salt-Sensitive Cardiovascular Changes in Mature Male Sprague Dawley Rats

Fructose and salt intake remain high, particularly in adolescents and young adults. The present studies were designed to evaluate the impact of high fructose and/or salt during pre- and early adolescence on salt sensitivity, blood pressure, arterial compliance, and left ventricular (LV) function in maturity. Male 5-week-old Sprague Dawley rats were studied over three 3-week phases (Phases I, II, and III). Two reference groups received either 20% glucose + 0.4% NaCl (GCS-GCS) or 20% fructose + 4% NaCl (FHS-FHS) throughout this study. The two test groups ingested fructose + 0.4% NaCl (FCS) or FHS during Phase I, then GCS in Phase II, and were then challenged with 20% glucose + 4% NaCl (GHS) in Phase III: FCS-GHS and FHS-GHS, respectively. Compared with GCS-GCS, systolic and mean pressures were significantly higher at the end of Phase III in all groups fed fructose during Phase I. Aortic pulse wave velocity (PWV) was elevated at the end of Phase I in FHS-GHS and FHS-FHS (vs. GCS-GCS). At the end of Phase III, PWV and renal resistive index were higher in FHS-GHS and FHS-FHS vs. GCS-GCS. Diastolic, but not systolic, LV function was impaired in the FHS-GHS and FHS-FHS but not FCS-FHS rats. Consumption of 20% fructose by male rats during adolescence results in salt-sensitive hypertension in maturity. When ingested with a high-salt diet during this early plastic phase, dietary fructose also predisposes to vascular stiffening and LV diastolic dysfunction in later life.

Disturbed Glucose Metabolism and Left Ventricular Geometry in the General Population

Background: This study sought to investigate the prevalence and clinical outcome of left ventricular (LV) geometry in prediabetes and type 2 diabetes mellitus (T2DM) and the impact of glucose metabolism on the incidence of left ventricular hypertrophy (LVH). Methods: 15,010 subjects (35–74 years) of the population-based Gutenberg Health Study were categorized into euglycemia, prediabetes, and T2DM according to clinical and metabolic (HbA1c) information. Clinical outcome was assessed via structured follow-up. Results: The study comprised 12,121 individuals with euglycemia (81.6%), 1415 with prediabetes (9.5%), and 1316 with T2DM (8.9%). Prevalence of LVH increased from euglycemia (10.2%) over prediabetes (17.8%) to T2DM (23.8%). Prediabetes and T2DM were associated with increased LV mass index (prediabetes: β1.3 (95% CI 0.78–1.81), p < 0.0001; T2DM: β2.37 (95% CI 1.81; 2.92), p < 0.0001) independent of age, sex, and cardiovascular risk factors (CVRF). The frequency of LVH was related to the presence of T2DM (prevalence ratio (PR)T2DM 1.2 (95% CI 1.06–1.35), p = 0.0038). T2DM was related to mortality independent of age, sex, and CVRF regardless of LVH (hazard ratio (HR)T2DM-LVH 2.67 (95% CI 1.94–3.66), p < 0.0001; HRT2DM-noLVH 1.59 (95% CI 1.29–1.96), p < 0.0001), prediabetes was only associated with outcome in individuals with LVH independent of age and sex (HRprediabetes-LVH 1.51 (95% CI 1.01–2.25), p = 0.045). Neither T2DM nor prediabetes were predictors of incident LVH after adjustment for clinical covariates. Conclusions: Prediabetes and T2DM promote alterations of cardiac geometry. T2DM and particularly the coprevalence of T2DM with LVH substantially reduce life expectancy. These findings highlight the need for new therapeutic and screening approaches to prevent and detect cardiometabolic diseases at an early stage.

Protective Effects of Huangqi Shengmai Yin on Type 1 Diabetes-Induced Cardiomyopathy by Improving Myocardial Lipid Metabolism

Diabetic cardiomyopathy (DCM) is one of the many complications of diabetes. DCM leads to cardiac insufficiency and myocardial remodeling and is the main cause of death in diabetic patients. Abnormal lipid metabolism plays an important role in the occurrence and development of DCM. Huangqi Shengmai Yin (HSY) has previously been shown to alleviate signs of heart disease. Here, we investigated whether HSY could improve cardiomyopathy caused by type 1 diabetes mellitus (T1DM) and improve abnormal lipid metabolism in the diabetic heart. Streptozotocin (STZ) was used to establish the T1DM mouse model, and T1DM mice were subsequently treated with HSY for eight weeks. The changes in the cardiac conduction system, histopathology, blood myocardial injury indices, and lipid content and expression of proteins related to lipid metabolism were evaluated. Our results showed that HSY could improve electrocardiogram; decrease the serum levels of CK-MB, LDH, and BNP; alleviate histopathological changes in cardiac tissue; and decrease myocardial lipid content in T1DM mice. These results indicate that HSY has a protective effect against T1DM-induced myocardial injury in mice and that this effect may be related to the improvement in myocardial lipid metabolism.

Diabetes-induced changes in cardiac voltage-gated ion channels

Diabetes mellitus affects the heart through various mechanisms such as microvascular defects, metabolic abnormalities, autonomic dysfunction and incompatible immune response. Furthermore, it can also cause functional and structural changes in the myocardium by a disease known as diabetic cardiomyopathy (DCM) in the absence of coronary artery disease. As DCM progresses it causes electrical remodeling of the heart, left ventricular dysfunction and heart failure. Electrophysiological changes in the diabetic heart contribute significantly to the incidence of arrhythmias and sudden cardiac death in diabetes mellitus patients. In recent studies, significant changes in repolarizing K⁺ currents, Na⁺ currents and L-type Ca²⁺ currents along with impaired Ca²⁺ homeostasis and defective contractile function have been identified in the diabetic heart. In addition, insulin levels and other trophic factors change significantly to maintain the ionic channel expression in diabetic patients. There are many diagnostic tools and management options for DCM, but it is difficult to detect its development and to effectively prevent its progress. In this review, diabetes-associated alterations in voltage-sensitive cardiac ion channels are comprehensively assessed to understand their potential role in the pathophysiology and pathogenesis of DCM.

Ultrasound-targeted microbubble destruction promotes myocardial angiogenesis and functional improvements in rat model of diabetic cardiomyopathy

BACKGROUND

Microvascular insufficiency plays an important role in the development of diabetic cardiomyopathy (DCM), therapeutic angiogenesis has been mainly used for the treatment of ischemic diseases. This study sought to verify the preclinical performance of SonoVue microbubbles (MB) combined ultrasound (US) treatment on myocardial angiogenesis in the rat model of DCM and investigate the optimal ultrasonic parameters.

METHODS

The male Sprague-Dawley (SD) rats were induced DCM by streptozotocin through intraperitoneal injecting and fed with high-fat diet. After the DCM model was established, the rats were divided into the normal group, DCM model group, and US + MB group, while the US + MB group was divided into four subsets according to different pulse lengths (PL) (8 cycles;18 cycle;26 cycle; 36 cycle). After all interventions, all rats underwent conventional echocardiography to examine the cardiac function. The rats were sacrificed and myocardial tissue was examined by histology and morphometry evaluations to detect the myocardial protective effect of SonoVue MBs using US techniques.

RESULTS

From morphologic observation and echocardiography, the DCM rats had a series of structural abnormalities of cardiac myocardium compared to the normal rats. The US-MB groups exerted cardioprotective effect in DCM rats, improved reparative neovascularization and increased cardiac perfusion, while the 26 cycle group showed significant therapeutic effects on the cardiac functions in DCM rats.

CONCLUSION

This strategy using SonoVue MB and US can improve the efficacy of angiogenesis, even reverse the progress of cardiac dysfunction and pathological abnormalities, especially using the 26 cycle parameters. Under further study, this combined strategy might provide a novel approach for early intervention of DCM in diabetic patients.

Diet-induced rodent models of obesity-related metabolic disorders-A guide to a translational perspective

Diet is a critical element determining human health and diseases, and unbalanced food habits are major risk factors for the development of obesity and related metabolic disorders. Despite technological and pharmacological advances, as well as intensification of awareness campaigns, the prevalence of metabolic disorders worldwide is still increasing. Thus, novel therapeutic approaches with increased efficacy are urgently required, which often depends on cellular and molecular investigations using robust animal models. In the absence of perfect rodent models, those induced by excessive consumption of fat and sugars better replicate the key aspects that are the root causes of human metabolic diseases. However, the results obtained using these models cannot be directly compared, particularly because of the use of different dietary protocols, and animal species and strains, among other confounding factors. This review article revisits diet-induced models of obesity and related metabolic disorders, namely, metabolic syndrome, prediabetes, diabetes and nonalcoholic fatty liver disease. A critical analysis focused on the main pathophysiological features of rodent models, as opposed to the criteria defined for humans, is provided as a practical guide with a translational perspective for the establishment of animal models of obesity-related metabolic diseases.

Blueberry Consumption Challenges Hepatic Mitochondrial Bioenergetics and Elicits Transcriptomics Reprogramming in Healthy Wistar Rats

An emergent trend of blueberries’ (BB) “prophylactic” consumption, due to their phytochemicals’ richness and well-known health-promoting claims, is widely scaled-up. However, the benefits arising from BB indiscriminate intake remains puzzling based on incongruent preclinical and human data. To provide a more in-depth elucidation and support towards a healthier and safer consumption, we conducted a translation-minded experimental study in healthy Wistar rats that consumed BB in a juice form (25 g/kg body weight (BW)/day; 14 weeks’ protocol). Particular attention was paid to the physiological adaptations succeeding in the gut and liver tissues regarding the acknowledged BB-induced metabolic benefits. Systemically, BB boosted serum antioxidant activity and repressed the circulating levels of 3-hydroxybutyrate (3-HB) ketone bodies and 3-HB/acetoacetate ratio. Moreover, BB elicited increased fecal succinic acid levels without major changes on gut microbiota (GM) composition and gut ultra-structural organization. Remarkably, an accentuated hepatic mitochondrial bioenergetic challenge, ensuing metabolic transcriptomic reprogramming along with a concerted anti-inflammatory pre-conditioning, was clearly detected upon long-term consumption of BB phytochemicals. Altogether, the results disclosed herein portray a quiescent mitochondrial-related metabolomics and hint for a unified adaptive response to this nutritional challenge. The beneficial or noxious consequences arising from this dietary trend should be carefully interpreted and necessarily claims future research.

Mitochondrial Dysfunction in Diabetic Cardiomyopathy: The Possible Therapeutic Roles of Phenolic Acids

As the powerhouse of the cells, mitochondria play a very important role in ensuring that cells continue to function. Mitochondrial dysfunction is one of the main factors contributing to the development of cardiomyopathy in diabetes mellitus. In early development of diabetic cardiomyopathy (DCM), patients present with myocardial fibrosis, dysfunctional remodeling and diastolic dysfunction, which later develop into systolic dysfunction and eventually heart failure. Cardiac mitochondrial dysfunction has been implicated in the development and progression of DCM. Thus, it is important to develop novel therapeutics in order to prevent the progression of DCM, especially by targeting mitochondrial dysfunction. To date, a number of studies have reported the potential of phenolic acids in exerting the cardioprotective effect by combating mitochondrial dysfunction, implicating its potential to be adopted in DCM therapies. Therefore, the aim of this review is to provide a concise overview of mitochondrial dysfunction in the development of DCM and the potential role of phenolic acids in combating cardiac mitochondrial dysfunction. Such information can be used for future development of phenolic acids as means of treating DCM by alleviating the cardiac mitochondrial dysfunction.

Urtica Pilulifera in Treating Pre-diabetic Rat Model to Control the Blood Glucose, Lipids and Oxidative Stress

Introduction:

Pre-diabetic precedes the development of full diabetes. Studying and identification changes in pre-diabetic conditions can give the possibility to decline the development of diabetes and treat conditions associated with diabetes such as cardiovascular diseases.

Aim:

The main objectives of the present study were to investigate the potential of using Urtica pilulifera in treating the pre-diabetic rat model and to investigate its anti-oxidant impact.

Methods:

The pre-diabetic model was induced in rats through daily giving high sucrose diet (35%) for 30 days. The extraction of U. pilulifera leaves was made as described by previous studies. Thirty male Wistar rats were randomly divided into three groups, control group (n=10), pre-diabetic group (n=10), and treated group with the extract of U. pilulifera (n=10). Control group rats received standard diet; pre-diabetic group rats received standard diet and high sucrose (35%) in drinking water, treated group rats received the same conditions as a pre-diabetic group, with intra-peritoneal injection of U. pilulifera injection on daily basis. After one month experiment, blood samples were taken from all rats and tested for glucose, triglycerides, cholesterol, GSH, TAC, and MDA.

Results:

Both glucose and triglycerides levels were significantly increased in pre-diabetic groups, and significantly reduced in the treated group by the extract of U.pilulifera. The cholesterol level was not significantly changed in all groups. The levels of GSH were significantly reduced in the pre-diabetic group compared with the control group. Treatment with the extract of U. pilulifera increased the levels of GSH significantly compared with the pre-diabetic group. The levels of TAC were not significantly changed between the control group and the pre-diabetic group, but significantly increased in the treated group compared with the pre-diabetic group. The levels of MDA significantly increased in the pre-diabetic group compared with the control group, and significantly reduced in the treated group compared with the control group.

Conclusion:

High sucrose pre-diabetic model is a good model to study diabetes at early stages, and the treatment using U. pilulifera has several benefits in reducing glucose and lipid profile lipids as well as combating oxidative stress.

Expression profiling of circular RNAs and their potential role in early‑stage diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a severe cardiovascular complication of diabetes mellitus (DM). Detecting DCM during the early stages of the disease remains a challenge, as the molecular mechanisms underlying early‑stage DCM are not clearly understood. Circular RNA (circRNA), a type of non‑coding RNA, has been confirmed to be associated with numerous diseases. However, it is still unclear how circRNAs are involved in early‑stage DCM. In the present study, heart tissues harvested from BKS‑db/db knock‑out mice were identified through high‑throughput RNA sequencing technology. A total of 58 significantly differentially expressed circRNAs were identified in the db/db sample. Among these, six upregulated circRNAs and seven downregulated circRNAs were detected by reverse transcription‑quantitative PCR and analyzed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. Furthermore, based on the predicted binding site with microRNAs (miRNAs) involved in DCM, five circRNAs (mmu_circ_0000652, mmu_circ_0000547, mmu_circ_0001058, mmu_circ_0000680 and novel_circ_0004285) were shown to serve as competing endogenous (ce)RNAs. The corresponding miRNAs and mRNAs of the ceRNAs were also verified, and two promising circRNA‑miRNA‑mRNA regulatory networks were determined. Finally, internal ribosome entry site prediction combined with open reading frame prediction indicated that it was highly possible that mmu_circ_0001160 encoded a protein. In the present study, a comprehensive analysis of the circRNA expression profile during the early phase of DCM was performed, and two promising circRNA‑miRNA‑mRNA regulatory networks were identified. These results lay the foundation for unravelling the underlying pathogenesis of DCM, and highlight potential biomarkers and therapeutic targets for the treatment of DCM at an early stage.

Adiponectin in onset and progression of T2DM with cardiac dysfunction in rats

Cardiovascular disease and type 2 diabetes mellitus (T2DM) patients have low level of adiponectin, however, till now the role of adiponectin in progression of ‘T2DM with cardiac dysfunction’ in animal model has not been characterized. Therefore, the aim of the present study was to develop and characterize T2DM animal model with cardiac dysfunction and to study the role of cardiac adiponectin expression in cardiac dysfunction. For this, Wistar rats (M/F) were fed a high-fat diet for different time periods: 3, 4 and 5 weeks and given a single, low-dose streptozotocin (25mg/kg), intraperitoneal injection 1 week prior to the experiments. Rats in T2DM group (3 weeks) developed hyperglycaemia, hyperlipidaemia, oxidative stress with normoinsulinaemia and mild cardiac dysfunction suggesting onset of T2DM with cardiac dysfunction. Extended high-fat feeding, that is, 4 and 5 weeks induced insulin resistance accompanied with cardiac hypertrophy, cardiac dysfunction and reduced baroreflex sensitivity indicating development of T2DM with cardiac dysfunction. Cardiac adiponectin expression did not change in rats of T2DM group (3 weeks), however, it significantly decreased in rats of two T2DM groups (4 and 5 weeks) along with increased intracellular adhesion molecule-1 levels. Thus, the present study for the first time indicates that in the present T2DM animal model, as T2DM progresses cardiac adiponectin expression also decreases which might be the precipitating factor for cardiac hypertrophy and decrease in baroreflex sensitivity, which induces cardiac dysfunction.

Crescent-Like Lesions as an Early Signature of Nephropathy in a Rat Model of Prediabetes Induced by a Hypercaloric Diet

Diabetic nephropathy (DN) is a major microvascular complication of diabetes. Obesity and hyperlipidemia, fueled by unhealthy food habits, are risk factors to glomerular filtration rate (GFR) decline and DN progression. Several studies recommend that diabetic patients should be screened early (in prediabetes) for kidney disease, in order to prevent advanced stages, for whom the current interventions are clearly inefficient. This ambition greatly depends on the existence of accurate early biomarkers and novel molecular targets, which only may arise with a more thorough knowledge of disease pathophysiology. We used a rat model of prediabetes induced by 23 weeks of high-sugar/high-fat (HSuHF) diet to characterize the phenotype of early renal dysfunction and injury. When compared with the control animals, HSuHF-treated rats displayed a metabolic phenotype compatible with obese prediabetes, displaying impaired glucose tolerance and insulin sensitivity, along with hypertriglyceridemia, and lipid peroxidation. Despite unchanged creatinine levels, the prediabetic animals presented glomerular crescent-like lesions, accompanied by increased kidney Oil-Red-O staining, triglycerides content and mRNA expression of IL-6 and iNOS. This model of HSuHF-induced prediabetes can be a useful tool to study early features of DN, namely crescent-like lesions, an early signature that deserves in-depth elucidation.

Exercise Training Promotes Cardiac Hydrogen Sulfide Biosynthesis and Mitigates Pyroptosis to Prevent High-Fat Diet-Induced Diabetic Cardiomyopathy

Obesity increases the risk of developing diabetes and subsequently, diabetic cardiomyopathy (DMCM). Reduced cardioprotective antioxidant hydrogen sulfide (H₂S) and increased inflammatory cell death via pyroptosis contribute to adverse cardiac remodeling and DMCM. Although exercise training (EX) has cardioprotective effects, it is unclear whether EX mitigates obesity-induced DMCM by increasing H₂S biosynthesis and mitigating pyroptosis in the heart. C57BL6 mice were fed a high-fat diet (HFD) while undergoing treadmill EX for 20 weeks. HFD mice developed obesity, hyperglycemia, and insulin resistance, which were reduced by EX. Left ventricle pressure-volume measurement revealed that obese mice developed reduced diastolic function with preserved ejection fraction, which was improved by EX. Cardiac dysfunction was accompanied by increased cardiac pyroptosis signaling, structural remodeling, and metabolic remodeling, indicated by accumulation of lipid droplets in the heart. Notably, EX increased cardiac H₂S concentration and expression of H₂S biosynthesis enzymes. HFD-induced obesity led to features of type 2 diabetes (T2DM), and subsequently DMCM. EX during the HFD regimen prevented the development of DMCM, possibly by promoting H₂S-mediated cardioprotection and alleviating pyroptosis. This is the first report of EX modulating H₂S and pyroptotic signaling in the heart.

Assessing the prevalence and risk factors of pre-diabetes among the community of Iganga municipality, Uganda: a cross sectional study

OBJECTIVE

The prevalence of pre-diabetes is increasing globally with more than 470 million people projected to develop pre-diabetes by 2030. In Africa, the average prevalence of pre-diabetes was estimated at 7.3% in 2015 and affected individual will develop type 2 diabetes mellitus within few decades. The aim of the study was to determine the prevalence of pre-diabetes and associated risk factors among residents of Iganga municipality. A cross-sectional study was conducted among males and females aged 13-60 years. District health office provided updated household list from which sampling of the villages was performed based on probability proportionate to population. Consented participants were prepared for the study, allowing fasting for 8 to 10 h before blood collection the next morning. Individuals with impaired fasting glucose, were subjected to OGTT.

RESULTS

130 participants were enrolled, of which 98 were women. The mean age of the participants was 35 years. The prevalence of pre-diabetes was 3.8%. The proportion of impaired glucose tolerance was higher in current smokers (p = 0.01), obese participants (p = 0.002) and hypertensive participants (p < 0.001). Prevalence of pre-diabetes is high in this community and is associated with current smoking, hypertension and high BMI.

Sexual stimulant effects of the mixture of Mondia whitei, Dracaena arborea, and Bridelia ferruginea in normal and prediabetic male Wistar rats

Background We investigated the effects of a polyherbal formulation prepared from the extracts of Mondia whitei (Periplocaceae), Dracaena arborea (Dracaenaceae), and Bridelia ferruginea (Euphorbiaceae) (MDB) on the sexual behavior of normal rats (NR) and prediabetic rats (PR). Methods Male Wistar rats were administered with drinking fructose solution (21%) or tap water for 16 weeks. After induction of prediabetic status, NR (n = 30) and PR (n = 30) were randomly distributed into 10 groups of six animals each and orally treated with distilled water (10 mL/kg), sildenafil citrate (5 mg/kg), or MDB (50, 100, or 500 mg/kg) for 21 days. Sexual behavior parameters per series (S) of ejaculation were evaluated on days 1, 7, 14, and 21. Results Drinking fructose solution (21%) induced prediabetic status in rats, characterized by a significant (p < 0.01) increase in glycemia by 43.41% compared with the control group. MDB improved sexual performances of NR and PR by increasing the mount frequency (MF) and the intromission frequency (IF) as well as the number of rats capable of ejaculating. For instance, the MF and the IF were significantly increased in animals administered with MDB for 7 (50 mg/kg, S1 and S2), 14 (100 mg/kg, S3), or 21 days (100 or 500 mg/kg, S2). This increase was more pronounced on days 7 and 14 in NR and PR treated with sildenafil citrate or MDB extracts, respectively. Conclusions The mixture of MDB improved sexual activity in NR and PR. This result may further justify the traditional use of these plants as sexual performance enhancers.

Piceatannol alleviates inflammation and oxidative stress via modulation of the Nrf2/HO-1 and NF-κB pathways in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is one of the leading causes of morbidity and mortality in diabetic patients. Piceatannol (PIC) has protective effects against cardiovascular disease; however, it remains unknown whether it also protects against DCM. A Cell Counting Kit-8 (CCK-8) assay was used to evaluate the effects of PIC on the viability of high glucose (HG)-induced H9C2 cells. Protein expression and mRNA levels were detected by western blotting and real-time polymerase chain reaction (RT-PCR), respectively. In vivo, physical and biochemical analyses, together with transthoracic echocardiography and hemodynamic measurements, were used to detect the effects of PIC treatment on cardiac function in DCM rats. Reactive oxygen species production was determined using an ELISA kit, and inflammatory cytokines were detected by RT-PCR. Pathological changes were assessed by hematoxylin-eosin staining, immunohistochemical staining, and TUNEL staining. According to the results, PIC treatment improved cell viability and inhibited cell apoptosis in HG-induced H9C2 cardiac myoblasts. In addition, PIC not only attenuated the over-production of interleukin-6 (IL-6) (P < 0.05) and tumor necrosis factor alpha (TNF-α) (P < 0.05), but also improved the expression of nuclear factor E2-related factor 2 (Nrf2) (P < 0.05) and heme oxygenase-1 (HO-1) (P < 0.01). Importantly, knockdown of Nrf2 suppressed PIC-mediated activation of the Nrf2/HO-1 pathway and abolished its anti-inflammatory effects. In vivo, oral administration of PIC suppressed STZ-induced inflammation, oxidative stress hypertrophy, fibrosis(myocardial collagen volume fraction in 5 mg/kg and 10 mg/kg PIC group was decreased 25.83% and 55.61% compared with the DM group), and apoptosis(Caspase-3 level in 5 mg/kg and 10 mg/kg PIC group was decreased 13.21% and 33.91% compared with the DM group), thereby relieving cardiac dysfunction and improving both fibrosis and pathological changes in cardiac tissues of diabetic rats. These findings define for the first time that the effects of PIC against DCM can be attributed to its role in inflammation and oxidative stress inhibition.

The prevalence of cardio-metabolic risk factors is differentially elevated in obesity-prone Osborne-Mendel and obesity-resistant S5B/Pl rats

AIMS

Individual susceptibility to develop obesity may impact the development of cardio-metabolic risk factors that lead to obesity-related comorbid conditions. Obesity-prone Osborne-Mendel (OM) rats expressed higher levels of visceral adipose inflammation than obesity-resistant, S5B/Pl (S5B) rats. However, the consumption of a high fat diet (HFD) differentially affected OM and S5B rats and induced an increase in visceral adipose inflammation in S5B rats. The current study examined the effects of HFD consumption on cardio-metabolic risk factors in OM and S5B rats.

MATERIALS & METHODS

Glucose regulation and circulating levels of lipids, adiponectin and C-reactive protein were assessed following 8 weeks of HFD or low fat diet (LFD) consumption. Left ventricle hypertrophy and mRNA expression of cardiovascular disease biomarkers were also quantified in OM and S5B rats.

KEY FINDINGS

Circulating levels of triglycerides were higher, while HDL cholesterol, adiponectin and glycemic control were lower in OM rats, compared to S5B rats. In the left ventricle, BNP and CTGF mRNA expression were higher in OM rats and IL-6, IL-1β, VEGF, and iNOS mRNA expression were higher in S5B rats.

SIGNIFICANCE

These findings support the hypothesis that cardio-metabolic risk factors are increased in obesity-prone individuals, which may increase the risk for the development of obesity-related comorbidities. In the current models, obesity-resistant S5B rats also exhibited cardiovascular risk factors supporting the importance of monitoring cardiovascular health in individuals characterized as obesity-resistant.

A high linoleic acid diet exacerbates metabolic responses and gut microbiota dysbiosis in obese rats with diabetes mellitus

Dietary polyunsaturated fatty acid (PUFA) levels may affect inflammatory responses and lipid metabolism.

Opening of mitoKATP improves cardiac function and inhibits apoptosis via the AKT-Foxo1 signaling pathway in diabetic cardiomyopathy

Decreasing phosphorylation of AKT-Foxo1 is closely associated with the onset of insulin resistance and apoptosis during diabetic cardiomyopathy (DCM). Opening of mitochondrial ATP-sensitive potassium channels (mitoK_ATP) increases the expression of p-AKT in the process of reperfusion injury. It was therefore hypothesized that opening of mitoK_ATP may regulate the AKT-Foxo1 signaling pathway and improve cardiac function in DCM. In the present study, opening of mitoK_ATP by diazoxide (DZX) was found to improve cardiac function and attenuate cardiomyocyte apoptosis in db/db mice. DZX also significantly increased the expression of p-AKT and p-Foxo1. Similarly, DZX decreased the expression of the heart failure marker NT-proBNP, increased mitochondrial membrane potential, inhibited apoptosis, and increased the expression of p-AKT and p-Foxo1 when mimicking insulin resistance in cultured cardiomyocytes. Moreover, the protective effects of DZX were completely blocked by the specific AKT inhibitor MK-2206. These data suggest that the regulation of the AKT-Foxo1 signaling pathway by mitoK_ATP plays an important role in improving cardiac function and inhibiting apoptosis in DCM, and may therefore be a new potential therapeutic target for DCM.

β Cell-specific deletion of guanylyl cyclase A, the receptor for atrial natriuretic peptide, accelerates obesity-induced glucose intolerance in mice

BACKGROUND

The cardiac hormones atrial (ANP) and B-type natriuretic peptides (BNP) moderate arterial blood pressure and improve energy metabolism as well as insulin sensitivity via their shared cGMP-producing guanylyl cyclase-A (GC-A) receptor. Obesity is associated with impaired NP/GC-A/cGMP signaling, which possibly contributes to the development of type 2 diabetes and its cardiometabolic complications. In vitro, synthetic ANP, via GC-A, stimulates glucose-dependent insulin release from cultured pancreatic islets and β-cell proliferation. However, the relevance for systemic glucose homeostasis in vivo is not known. To dissect whether the endogenous cardiac hormones modulate the secretory function and/or proliferation of β-cells under (patho)physiological conditions in vivo, here we generated a novel genetic mouse model with selective disruption of the GC-A receptor in β-cells.

METHODS

Mice with a floxed GC-A gene were bred to Rip-Cre^TG mice, thereby deleting GC-A selectively in β-cells (β GC-A KO). Weight gain, glucose tolerance, insulin sensitivity, and glucose-stimulated insulin secretion were monitored in normal diet (ND)- and high-fat diet (HFD)-fed mice. β-cell size and number were measured by immunofluorescence-based islet morphometry.

RESULTS

In vitro, the insulinotropic and proliferative actions of ANP were abolished in islets isolated from β GC-A KO mice. Concordantly, in vivo, infusion of BNP mildly enhanced baseline plasma insulin levels and glucose-induced insulin secretion in control mice. This effect of exogenous BNP was abolished in β GC-A KO mice, corroborating the efficient inactivation of the GC-A receptor in β-cells. Despite this under physiological, ND conditions, fasted and fed insulin levels, glucose-induced insulin secretion, glucose tolerance and β-cell morphology were similar in β GC-A KO mice and control littermates. However, HFD-fed β GC-A KO animals had accelerated glucose intolerance and diminished adaptative β-cell proliferation.

CONCLUSIONS

Our studies of β GC-A KO mice demonstrate that the cardiac hormones ANP and BNP do not modulate β-cell's growth and secretory functions under physiological, normal dietary conditions. However, endogenous NP/GC-A signaling improves the initial adaptative response of β-cells to HFD-induced obesity. Impaired β-cell NP/GC-A signaling in obese individuals might contribute to the development of type 2 diabetes.

Subtle thinning of retinal layers without overt vascular and inflammatory alterations in a rat model of prediabetes

PURPOSE

Diabetic retinopathy is a neurovascular disease characterized by increased permeability of the blood-retinal barrier, changes in the neural components of the retina, and low-grade chronic inflammation. Diabetic retinopathy is a major complication of diabetes; however, the impact of a prediabetic state on the retina remains to be elucidated. The aim of this study was to assess possible early retinal changes in prediabetic rats, by evaluating changes in the integrity of the blood-retinal barrier, the retinal structure, neural markers, and inflammatory mediators.

METHODS

Several parameters were analyzed in the retinas of Wistar rats that drank high sucrose (HSu; 35% sucrose solution during 9 weeks, the prediabetic animal model) and were compared with those of age-matched controls. The permeability of the blood-retinal barrier was assessed with the Evans blue assay, and the content of the tight junction proteins and neural markers with western blotting. Optical coherence tomography was used to evaluate retinal thickness. Cell loss at the ganglion cell layer was assessed with terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay and by evaluating the immunoreactivity of the Brn3a transcription factor. To assess retinal neuroinflammation, the mRNA expression and protein levels of inducible nitric oxide synthase isoform (iNOS), interleukin-1 beta (IL-1β), and tumor necrosis factor (TNF) were evaluated. Iba1 and MHC-II immunoreactivity and translocator protein (TSPO) mRNA levels were assessed to study the microglial number and activation state.

RESULTS

The thickness of the inner retinal layers of the HSu-treated animals decreased. Nevertheless, no apoptotic cells were observed, and no changes in retinal neural markers were detected in the retinas of the HSu-treated animals. No changes were detected in the permeability of the blood-retinal barrier, as well as the tight junction protein content between the HSu-treated rats and the controls. In addition, the inflammatory parameters remained unchanged in the retina despite the tendency for an increase in the number of retinal microglial cells.

CONCLUSIONS

In a prediabetic rat model, the retinal structure is affected by the thinning of the inner layers, without overt vascular and inflammatory alterations. The results suggest neuronal dysfunction (thinning of the inner retina) that may precede or anticipate the vascular and inflammatory changes. Subtle structural changes might be viewed as early disturbances in an evolving disease, suggesting that preventive strategies (such as the modification of diet habits) could be applied at this stage, before the progression toward irreversible dysfunction and damage to the retina.

Ameliorative effect of nicotine exposure on insulin resistance is accompanied by decreased cardiac glycogen synthase kinase-3 and plasminogen activator inhibitor-1 during oral oestrogen-progestin therapy

CONTEXT

Cigarette smoking is considered to be a major risk factor for the development of diabetes and cardiovascular disease. Oestrogen-progestin combined oral contraceptive (COC) use has been associated with adverse cardiometabolic events.

OBJECTIVE

We hypothesized that nicotine would ameliorate insulin resistance (IR) that is accompanied by decreased cardiac glycogen synthase kinase-3 (GSK-3) and plasminogen activator inhibitor-1 (PAI-1).

METHODS

Female Wistar rats received (po) low-(0.1 mg/kg) or high-nicotine (1.0 mg/kg) with or without COC containing 5.0 µg levonorgestrel plus 1.0 µg ethinylestradiol daily for 8 weeks.

RESULTS

Data showed that COC treatment or nicotine exposure led to IR, glucose deregulation, atherogenic dyslipidemia, increased corticosterone, aldosterone, cardiac and circulating GSK-3 values and PAI-1. However, these effects with the exception of corticosterone and aldosterone were ameliorated in COC + nicotine-exposed rats.

CONCLUSION

Amelioration of IR induced by COC treatment is accompanied by decreased circulating PAI-1, cardiac PAI-1 and GSK-3 instead of circulating aldosterone and corticosterone.

n-3 polyunsaturated fatty acids preventd-galactose-induced cognitive deficits in prediabetic rats

Nutritional deficit of n-3 polyunsaturated fatty acids (PUFAs) is closely related to cognitive impairment and depression in later life.

Clinical characteristics and risk factors for retinal diabetic neurodegeneration in type 2 diabetes

AIMS

To identify clinical characteristics and risk factors of retinal neurodegeneration represented by macular ganglion cell/inner plexiform layer (mGCIPL) thinning in patients with long-standing type 2 diabetes mellitus (T2DM).

METHODS

Patients who had T2DM for >15 years were prospectively recruited from September 2014 to July 2015. Clinical data and samples were collected according to the Common Data Element and Standards of Procedure developed by the Korean Diabetes Association research council. Baseline characteristics included age, gender, family history, medical record of comorbidity, and microvascular complications. All patients underwent optical coherence tomography with automatic segmentation of the mGCIPL in six parafoveal regions. Multivariable regression analysis identified factors associated with mGCIPL thinning.

RESULTS

Of 220 registered patients, 162 were included after ophthalmologic examination. The mean (SD) age was 65.0 (9.3) years, the mean duration of T2DM was 20.5 (4.0) years; mGCIPL thickness was 76.2 (8.5) µm. Hypertension, diabetic retinopathy, statin medication, estimated glomerular filtration rate, conduction velocity of the posterior tibial, peroneal, and sural nerves, and cardiac autonomic neuropathy (CAN) score were significantly correlated with mGCIPL thickness. Multivariate regression analysis showed that the CAN score (coefficient = -1.78, p = 0.001) and sural nerve velocity (coefficient = 0.458, p = 0.035) yielded a significant high regression correlation with mGCIPL thickness (overall R ² = 0.46).

CONCLUSIONS

This study demonstrated that various clinical features were associated with retinal neurodegeneration in T2DM. In particular, peripheral nerve conduction and autonomic nerve function were confirmed to be strong risk factors for mGCIPL thinning in patients with T2DM.

Glucose and Lipid Dysmetabolism in a Rat Model of Prediabetes Induced by a High-Sucrose Diet

Glucotoxicity and lipotoxicity are key features of type 2 diabetes mellitus, but their molecular nature during the early stages of the disease remains to be elucidated. We aimed to characterize glucose and lipid metabolism in insulin-target organs (liver, skeletal muscle, and white adipose tissue) in a rat model treated with a high-sucrose (HSu) diet. Two groups of 16-week-old male Wistar rats underwent a 9-week protocol: HSu diet (n = 10)-received 35% of sucrose in drinking water; Control (n = 12)-received vehicle (water). Body weight, food, and beverage consumption were monitored and glucose, insulin, and lipid profiles were measured. Serum and liver triglyceride concentrations, as well as the expression of genes and proteins involved in lipid biosynthesis were assessed. The insulin-stimulated glucose uptake and isoproterenol-stimulated lipolysis were also measured in freshly isolated adipocytes. Even in the absence of obesity, this rat model already presented the main features of prediabetes, with fasting normoglycemia but reduced glucose tolerance, postprandial hyperglycemia, compensatory hyperinsulinemia, as well as decreased insulin sensitivity (resistance) and hypertriglyceridemia. In addition, impaired hepatic function, including altered gluconeogenic and lipogenic pathways, as well as increased expression of acetyl-coenzyme A carboxylase 1 and fatty acid synthase in the liver, were observed, suggesting that liver glucose and lipid dysmetabolism may play a major role at this stage of the disease.

Diabetic cardiomyopathy: where we are and where we are going

The global burden of diabetes mellitus and its related complications are currently increasing. Diabetes mellitus affects the heart through various mechanisms including microvascular impairment, metabolic disturbance, subcellular component abnormalities, cardiac autonomic dysfunction, and a maladaptive immune response. Eventually, diabetes mellitus can cause functional and structural changes in the myocardium without coronary artery disease, a disorder known as diabetic cardiomyopathy (DCM). There are many diagnostic tools and management options for DCM, although it is difficult to detect its development and effectively prevent its progression. In this review, we summarize the current research regarding the pathophysiology and pathogenesis of DCM. Moreover, we discuss emerging diagnostic evaluation methods and treatment strategies for DCM, which may help our understanding of its underlying mechanisms and facilitate the identification of possible new therapeutic targets.

Diagnostic approaches for diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a cardiac dysfunction which affects approximately 12% of diabetic patients, leading to overt heart failure and death. However, there is not an efficient and specific methodology for DCM diagnosis, possibly because molecular mechanisms are not fully elucidated, and it remains asymptomatic for many years. Also, DCM frequently coexists with other comorbidities such as hypertension, obesity, dyslipidemia, and vasculopathies. Thus, human DCM is not specifically identified after heart failure is established. In this sense, echocardiography has been traditionally considered the gold standard imaging test to evaluate the presence of cardiac dysfunction, although other techniques may cover earlier DCM detection by quantification of altered myocardial metabolism and strain. In this sense, Phase-Magnetic Resonance Imaging and 2D/3D-Speckle Tracking Echocardiography may potentially diagnose and stratify diabetic patients. Additionally, this information could be completed with a quantification of specific plasma biomarkers related to related to initial stages of the disease. Cardiotrophin-1, activin A, insulin-like growth factor binding protein-7 (IGFBP-7) and Heart fatty-acid binding protein have demonstrated a stable positive correlation with cardiac hypertrophy, contractibility and steatosis responses. Thus, we suggest a combination of minimally-invasive diagnosis tools for human DCM recognition based on imaging techniques and measurements of related plasma biomarkers.

The role of natriuretic peptides in diabetes and its complications

This review aimed to summarize recent findings on the role of natriuretic peptides (NPs) in diabetes and its important complications. Although the treatment of diabetes mellitus has benefited from recent advances, aggressive glycemic control can increase the risk of hypoglycemia and weight gain. Therefore, innovative therapies are required to address this issue. Natriuretic peptides (NPs) may have such novel therapeutic potential. NPs comprise a family of structurally related peptides, including atrial, brain, C-type, and dendroaspis. Each of these NPs has a wide range of specific functions to regulate and maintain cardiovascular, renal, and endocrine homeostasis. NPs exert their effects by interacting with three receptor subtypes including NPR-A, NPR-B, and NPR-C. The coronary NP system has been suggested to be involved in regulating water and salt balance, as well as vascular remodeling. In this review, we provide evidence that NPs play an important role in diabetes mellitus and its related complications including macrovascular and microvascular disorders. NPs hold promise as markers for early diagnosis, risk assessment, and intervention guidance in diabetes and its complications and may thus improve diabetes care.

Using basic fibroblast growth factor nanoliposome combined with ultrasound-introduced technology to early intervene the diabetic cardiomyopathy

Basic fibroblast growth factor (bFGF)-loaded liposome (bFGF-lip) combined with ultrasound-targeted microbubble destruction (UTMD) technique was investigated to prevent diabetic cardiomyopathy (DCM). Cardiac function and myocardial ultrastructure were assessed. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) staining, immunohistochemistry staining, and Western blot assay were used to investigate the signal pathway underlying the expression of bFGF in DCM treatment. From Mason staining and TUNEL staining, bFGF-lip + UTMD group showed significant differences from the diabetes group and other groups treated with bFGF or bFGF-lip. The diabetes group showed similar results (myocardial capillary density, collagen volume fraction, and cardiac myocyte apoptosis index) to other bFGF treatment groups. Indexes from transthoracic echocardiography and hemodynamic evaluation also proved the same conclusion. These results confirmed that the abnormalities including diastolic dysfunctions, myocardial fibrosis, and metabolic disturbances could be suppressed by the different extents of twice-weekly bFGF treatments for 12 consecutive weeks (free bFGF or bFGF-lip +/− UTMD), with the strongest improvements observed in the bFGF-lip + UTMD group. The group combining bFGF-lip with UTMD demonstrated the highest level of bFGF expression among all the groups. The bFGF activated the PI3K/AKT signal pathway, causing the reduction of myocardial cell apoptosis and increase of microvascular density. This strategy using bFGF-lip and UTMD is a potential strategy in early intervention of DCM in diabetes.

Prediabetes Enhances Periodontal Inflammation Consistent With Activation of Toll-Like Receptor-Mediated Nuclear Factor-κB Pathway in Rats

BACKGROUND

Clinical studies have showed that prediabetes (preDM) is a predisposing factor for periodontitis. However, the pathogenic mechanism involved is unclear. Because it is known that the activation of Toll-like receptor (TLR)-mediated nuclear factor-kappa B (NF-κB) signaling pathway plays a crucial role in periodontitis, it is hypothesized that preDM enhances periodontal inflammation by activation of the TLR-mediated NF-κB pathway.

METHODS

In this study, a preDM rat model is established by feeding a high-fat diet (HFD). HFD-induced rats with preDM (n = 7) and normal chow-fed rats (n = 7) were studied. The animal model was characterized in terms of body weight and the glycemic and insulinemic profiles. The following parameters were assessed to evaluate possible early periodontal alterations and underlying mechanisms: 1) histology analysis of periodontal tissue; and 2) serum and mRNA levels and/or the tissue protein expression of TLRs, myeloid differentiation factor 88 (MyD88), tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), NF-κB, cytokines, advanced glucose ends (AGEs), and free fatty acids (FFAs).

RESULTS

Rats with preDM presented higher expression of TLR2 and TLR4 in periodontal tissue in the HFD group compared with the control group. The TLR2 and TLR4 was mostly expressed in gingiva, and TLR4 was expressed in periodontal ligament in rats. Furthermore, the MyD88 and TRAF6 protein levels were significantly increased in gingiva in rats with preDM compared with normal rats. The activity of NF-κB signals was higher in rats with preDM than in normal rats. Regarding cytokines expression, the TNF-α protein levels and interleukin-1β mRNA levels were significantly increased in the HFD group compared with the control group. In the serum, AGEs levels were significantly increased in the rats with preDM. Mean FFAs concentrations were increased in rats with preDM compared with normal rats, but it did not reach statistical significance.

CONCLUSION

In rats with preDM, TLR2 and TLR4 gene and protein levels were higher in periodontal tissue, and the activation of NF-κB may, through TLRs/MyD88, cause more cytokine secretion, which is associated with the onset or development of periodontal disease.

Dexrazoxane protects breast cancer patients with diabetes from chemotherapy-induced cardiotoxicity

BACKGROUND

To evaluate the cardioprotective effect of dexrazoxane (DEX) on chemotherapy in patients with breast cancer with concurrent type 2 diabetes mellitus (DM2).

METHODS

Eighty female patients with breast cancer with DM2 were randomly assigned to receive chemotherapy only or chemotherapy plus DEX. All patients received 80 mg/m epirubicin and 500 mg/m cyclophosphamide by intravenous infusion every 3 weeks for a total of 6 cycles. The group assigned to receive chemotherapy alone received placebo 30 minutes before epirubicin administration. The group assigned to receive chemotherapy plus DEX received 800 mg/m DEX 30 minutes before epirubicin administration. Cardiac function and hematology before and after 6 cycles of chemotherapy were analyzed.

RESULTS

There was no difference in baseline systole or diastole function between the 2 DM2 groups. Patients receiving chemotherapy alone experienced significantly greater reductions in Ea and significantly greater elevations in E/Ea and Tei index in comparison with patients receiving chemotherapy plus DEX. After chemotherapy, superoxide dismutase was significantly reduced, and serum malondialdehyde (MDA) was significantly increased in patients with DM2. Serum superoxide dismutase levels were comparable between the 2 groups before and after chemotherapy, MDA levels were comparable between the 2 groups before chemotherapy, whereas serum MDA was significantly higher after chemotherapy in the chemotherapy alone group in comparison with the group that received DEX.

CONCULSIONS

DEX protects against cardiotoxicity induced by chemotherapy in patients with breast cancer with concurrent DM2.

Effects of exercise training on stress-induced vascular reactivity alterations: role of nitric oxide and prostanoids

BACKGROUND

Physical exercise may modify biologic stress responses.

OBJECTIVE

To investigate the impact of exercise training on vascular alterations induced by acute stress, focusing on nitric oxide and cyclooxygenase pathways.

METHOD

Wistar rats were separated into: sedentary, trained (60-min swimming, 5 days/week during 8 weeks, carrying a 5% body-weight load), stressed (2 h-immobilization), and trained/stressed. Response curves for noradrenaline, in the absence and presence of L-NAME or indomethacin, were obtained in intact and denuded aortas (n = 7-10).

RESULTS

None of the procedures altered the denuded aorta reactivity. Intact aortas from stressed, trained, and trained/stressed rats showed similar reduction in noradrenaline maximal responses (sedentary 3.54 ± 0.15, stressed 2.80 ± 0.10*, trained 2.82 ± 0.11*, trained/stressed 2.97 ± 0.21*, *P < 0.05 relate to sedentary). Endothelium removal and L-NAME abolished this hyporeactivity in all experimental groups, except in trained/stressed rats that showed a partial aorta reactivity recovery in L-NAME presence (L-NAME: sedentary 5.23 ± 0,26#, stressed 5.55 ± 0.38#, trained 5.28 ± 0.30#, trained/stressed 4.42 ± 0.41, #P < 0.05 related to trained/stressed). Indomethacin determined a decrease in sensitivity (EC50) in intact aortas of trained rats without abolishing the aortal hyporeactivity in trained, stressed, and trained/stressed rats.

CONCLUSIONS

Exercise-induced vascular adaptive response involved an increase in endothelial vasodilator prostaglandins and nitric oxide. Stress-induced vascular adaptive response involved an increase in endothelial nitric oxide. Beside the involvement of the endothelial nitric oxide pathway, the vascular response of trained/stressed rats involved an additional mechanism yet to be elucidated. These findings advance on the understanding of the vascular processes after exercise and stress alone and in combination.

Excess perigestational folic acid exposure induces metabolic dysfunction in post-natal life

The aim of this study was to understand whether high folic acid (HFA) exposure during the perigestational period induces metabolic dysfunction in the offspring, later in life. To do this, female Sprague-Dawley rats (G0) were administered a dose of folic acid (FA) recommended for pregnancy (control, C, 2 mg FA/kg of diet, n=5) or a high dose of FA (HFA, 40 mg FA/kg of diet, n=5). Supplementation began at mating and lasted throughout pregnancy and lactation. Body weight and food and fluid intake were monitored in G0 and their offspring (G1) till G1 were 13 months of age. Metabolic blood profiles were assessed in G1 at 3 and 13 months of age (3M and 13M respectively). Both G0 and G1 HFA females had increased body weight gain when compared with controls, particularly 22 (G0) and 10 (G1) weeks after FA supplementation had been stopped. G1 female offspring of HFA mothers had increased glycemia at 3M, and both female and male G1 offspring of HFA mothers had decreased glucose tolerance at 13M, when compared with matched controls. At 13M, G1 female offspring of HFA mothers had increased insulin and decreased adiponectin levels, and G1 male offspring of HFA mothers had increased levels of leptin, when compared with matched controls. In addition, feeding of fructose to adult offspring revealed that perigestational exposure to HFA renders female progeny more susceptible to developing metabolic unbalance upon such a challenge. The results of this work indicate that perigestational HFA exposure the affects long-term metabolic phenotype of the offspring, predisposing them to an insulin-resistant state.

Updating experimental models of diabetic cardiomyopathy

Diabetic cardiomyopathy entails a serious cardiac dysfunction induced by alterations in structure and contractility of the myocardium. This pathology is initiated by changes in energy substrates and occurs in the absence of atherothrombosis, hypertension, or other cardiomyopathies. Inflammation, hypertrophy, fibrosis, steatosis, and apoptosis in the myocardium have been studied in numerous diabetic experimental models in animals, mostly rodents. Type I and type II diabetes were induced by genetic manipulation, pancreatic toxins, and fat and sweet diets, and animals recapitulate the main features of human diabetes and related cardiomyopathy. In this review we update and discuss the main experimental models of diabetic cardiomyopathy, analysing the associated metabolic, structural, and functional abnormalities, and including current tools for detection of these responses. Also, novel experimental models based on genetic modifications of specific related genes have been discussed. The study of specific pathways or factors responsible for cardiac failures may be useful to design new pharmacological strategies for diabetic patients.

Emodin protects against diabetic cardiomyopathy by regulating the AKT/GSK-3β signaling pathway in the rat model

Diabetes mellitus (DM) has been recognized as a major health problem. Emodin (Emo) has been reported to exhibit protective effects against diabetic nephropathy. However, little has been known about the effect of Emo on diabetic cardiomyopathy (DCM). A type 2 DM model was induced in rats by low dose streptozotocin (STZ) combined with high energy intake. We found that Emo-treated groups displayed significantly higher body weight (BW) and lower heart weight (HW)/BW. Furthermore, Emo could significantly decrease blood glucose, total cholesterol (TG) levels, and triglyceride (TC) levels in diabetic rats. Moreover, the Emo-treated group showed a marked increase in heart rate (HR) and showed lower left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular posterior wall thickness (LWPWT), and interventricular septal diastolic wall thickness (IVSD). Emo induced a significant increase in phosphorylation of Akt and GSK-3β in myocardium. These results suggest that Emo may have great therapeutic potential in the treatment of DCM by Akt/GSK-3β signaling pathway.

Chronic variable stress improves glucose tolerance in rats with sucrose-induced prediabetes

The incidence of type-2 diabetes (T2D) and the burden it places on individuals, as well as society as a whole, compels research into the causes, factors and progression of this disease. Epidemiological studies suggest that chronic stress exposure may contribute to the development and progression of T2D in human patients. To address the interaction between chronic stress and the progression of T2D, we developed a dietary model of the prediabetic state in rats utilizing unlimited access to 30% sucrose solution (in addition to unlimited access to normal chow and water), which led to impaired glucose tolerance despite elevated insulin levels. We then investigated the effects of a chronic variable stress paradigm (CVS; twice daily exposure to an unpredictable stressor for 2 weeks) on metabolic outcomes in this prediabetic model. Chronic stress improved glucose tolerance in prediabetic rats following a glucose challenge. Importantly, pair-fed control groups revealed that the beneficial effect of chronic stress did not result from the decreased food intake or body weight gain that occurred during chronic stress. The present work suggests that chronic stress in rodents can ameliorate the progression of diet-induced prediabetic disease independent of chronic stress-induced decreases in food intake and body weight.