Diastolic dysfunction in spontaneous type 2 diabetes rhesus monkeys: a study using echocardiography and magnetic resonance imaging

Echocardiographic characterization of age- and sex-associated differences in cardiac function and morphometry in nonhuman primates

Aging per se is a major risk factor for cardiovascular diseases and is associated with progressive changes in cardiac structure and function. Rodent models are commonly used to study cardiac aging, but do not closely mirror differences as they occur in humans. Therefore, we performed a 2D echocardiographic study in non-human primates (NHP) to establish age- and sex-associated differences in cardiac function and morphometry in this animal model. M mode and 2D echocardiography and Doppler analyses were performed cross-sectionally in 38 healthy rhesus monkeys (20 females and 18 males), both young (age 7-12 years; n = 20) and old (age 19-30 years; n = 18). The diameters of the cardiac chambers did not differ significantly by age group, but males had larger left ventricular diameters (2.43 vs 2.06 cm in diastole and 1.91 vs 1.49 cm in systole, p = 0.0004 and p = 0.0001, respectively) and left atrial diameter (1.981 vs 1.732 cm; p = 0.0101). Left ventricular mass/body surface area did not vary significantly with age and sex. Ejection fraction did not differ by age and females presented a higher ejection fraction than males (54.0 vs 50.8%, p = 0.0237). Diastolic function, defined by early to late mitral peak flow velocity ratio (E/A), was significantly lower in old rhesus monkeys (2.31 vs 1.43, p = 0.0020) and was lower in females compared to males (1.595 vs 2.230, p = 0.0406). Right ventricular function, evaluated by measuring the Tricuspid Annular Plane Systolic Excursion, did not differ by age or sex, and Right Ventricular Free Wall Longitudinal Strain, did not differ with age but was lower in males than in females (-22.21 vs -17.95%, p = 0.0059). This is the first echocardiographic study to evaluate age- and sex-associated changes of cardiac morphometry and function in young and old NHP. The findings of this work will provide a reference to examine the effect of age and sex on cardiac diseases in NHP.

Large animal models to study effectiveness of therapy devices in the treatment of heart failure with preserved ejection fraction (HFpEF)

Our understanding of the complex pathophysiology of Heart failure with preserved ejection fraction (HFpEF) is limited by the lack of a robust in vivo model. Existing in-vivo models attempt to reproduce the four main phenotypes of HFpEF; ageing, obesity, diabetes mellitus and hypertension. To date, there is no in vivo model that represents all the haemodynamic characteristics of HFpEF, and only a few have proven to be reliable for the preclinical evaluation of potentially new therapeutic targets. HFpEF accounts for 50% of all the heart failure cases and its incidence is on the rise, posing a huge economic burden on the health system. Patients with HFpEF have limited therapeutic options available. The inadequate effectiveness of current pharmaceutical therapeutics for HFpEF has prompted the development of device-based treatments that target the hemodynamic changes to reduce the symptoms of HFpEF. However, despite the potential of device-based solutions to treat HFpEF, most of these therapies are still in the developmental stage and a relevant HFpEF in vivo model will surely expedite their development process. This review article outlines the major limitations of the current large in-vivo models in use while discussing how these designs have helped in the development of therapy devices for the treatment of HFpEF.

Imaging characterization of myocardial function, fibrosis, and perfusion in a nonhuman primate model with heart failure-like features

Introduction

The availability of a human-like chronic heart failure (HF) animal model was critical for affiliating development of novel therapeutic drug treatments. With the close physiology relatedness to humans, the non-human primate (NHP) HF model would be valuable to better understand the pathophysiology and pharmacology of HF. The purpose of this work was to present preliminary cardiac image findings using echocardiography and cardiovascular magnetic resonance (CMR) in a HF-like cynomolgus macaque model.

Methods

The NHP diet-induced model developed cardiac phenotypes that exhibited diastolic dysfunction with reduced left ventricular ejection fraction (LVEF) or preserved LVEF. Twenty cynomolgus monkeys with cardiac dysfunction were selected by echocardiography and subsequently separated into two groups, LVEF < 65% (termed as HFrEF, n = 10) and LVEF ≥ 65% with diastolic dysfunction (termed as HFpEF, n = 10). Another group of ten healthy monkeys was used as the healthy control. All monkeys underwent a CMR study to measure global longitudinal strain (GLS), myocardial extracellular volume (ECV), and late gadolinium enhancement (LGE). In healthy controls and HFpEF group, quantitative perfusion imaging scans at rest and under dobutamine stress were performed and myocardial perfusion reserve (MPR) was subsequently obtained.

Results

No LGE was observed in any monkey. Monkeys with HF-like features were significantly older, compared to the healthy control group. There were significant differences among the three groups in ECV (20.79 ± 3.65% in healthy controls; 27.06 ± 3.37% in HFpEF group, and 31.11 ± 4.50% in HFrEFgroup, p < 0.001), as well as for stress perfusion (2.40 ± 0.34 ml/min/g in healthy controls vs. 1.28 ± 0.24 ml/min/g in HFpEF group, p < 0.01) and corresponding MPR (1.83 ± 0.3 vs. 1.35 ± 0.29, p < 0.01). After adjusting for age, ECV (p = 0.01) and MPR (p = 0.048) still showed significant differences among the three groups.

Conclusion

Our preliminary imaging findings demonstrated cardiac dysfunction, elevated ECV, and/or reduced MPR in this HF-like NHP model. This pilot study laid the foundation for further mechanistic research and the development of a drug testing platform for distinct HF pathophysiology.

Replacement substance P reduces cardiac fibrosis in monkeys with type 2 diabetes

BACKGROUND

Type 2 diabetes mellitus (T2DM)-associated cardiac fibrosis contributes to heart failure. We previously showed that diabetic mice with cardiomyopathy, including cardiac fibrosis, exhibit low levels of the neuropeptide substance P; exogenous replacement of substance P reversed cardiac fibrosis, independent of body weight, blood glucose and blood pressure. We sought to elucidate the effectiveness and safety of replacement substance P to ameliorate or reverse cardiac fibrosis in type 2 diabetic monkeys.

METHODS

Four female T2DM African Green monkeys receive substance P (0.5 mg/Kg/day S.Q. injection) for 8 weeks. We obtained cardiac magnetic resonance imaging and blood samples to assess left ventricular function and fibrosis by T1 map-derived extracellular volume as well as circulating procollagen type I C-terminal propeptide. Hematological parameters for toxicities were also assessed in these monkeys and compared with three female T2DM monkeys receiving saline S.Q. as a safety comparison group.

RESULTS

Diabetic monkeys receiving replacement substance P exhibited a ∼20% decrease in extracellular volume (p = 0.01), concomitant with ∼25% decrease procollagen type I C-terminal propeptide levels (p = 0.008). Left ventricular ejection fraction was unchanged with substance P (p = 0.42); however, circumferential strain was improved (p < 0.01). Complete blood counts, glycosylated hemoglobin A1c, lipids, liver and pancreatic enzymes, and inflammation markers were unchanged (p > 0.05).

CONCLUSIONS

Replacement substance P reversed cardiac fibrosis in a large preclinical model of type 2 diabetes, independent of glycemic control. No hematological or organ-related toxicity was associated with replacement substance P. These results strongly support a potential application for replacement substance P as safe therapy for diabetic cardiac fibrosis.

Alterations in Microbiota and Metabolites Related to Spontaneous Diabetes and Pre-Diabetes in Rhesus Macaques

Spontaneous type 2 diabetes mellitus (T2DM) macaques are valuable resources for our understanding the pathological mechanism of T2DM. Based on one month’s fasting blood glucose survey, we identified seven spontaneous T2DM macaques and five impaired glucose regulation (IGR) macaques from 1408 captive individuals. FPG, HbA1c, FPI and IR values were significant higher in T2DM and IGR than in controls. 16S rRNA sequencing of fecal microbes showed the significantly greater abundance of Oribacterium, bacteria inhibiting the production of secondary bile acids, and Phascolarctobacterium, bacteria producing short-chain fatty acids was significantly lower in T2DM macaques. In addition, several opportunistic pathogens, such as Mogibacterium and Kocuria were significantly more abundant in both T2DM and IGR macaques. Fecal metabolites analysis based on UHPLC-MS identified 50 differential metabolites (DMs) between T2DM and controls, and 26 DMs between IGR and controls. The DMs were significantly enriched in the bile acids metabolism, fatty acids metabolism and amino acids metabolism pathways. Combining results from physiochemical parameters, microbiota and metabolomics, we demonstrate that the imbalance of gut microbial community leading to the dysfunction of glucose, bile acids, fatty acids and amino acids metabolism may contribute to the hyperglycaemia in macaques, and suggest several microbes and metabolites are potential biomarkers for T2DM and IGR macaques.

Antidiabetic effect of an engineered bacterium Lactobacillus plantarum-pMG36e -GLP-1 in monkey model

Glucagon-like peptide-1 (GLP-1) reduces postprandial hyperglycaemia, but its short half-life inhibits clinical application. The aim of the current study was to evaluate the treatment efforts of an engineered strain, Lactobacillus plantarum-pMG36e-GLP-1 (L. plantarum-pMG36e-GLP-1), that continuously expresses GLP-1 in spontaneous type 2 diabetes mellitus (T2DM) monkeys. After 7 weeks of oral supplementation with L. plantarum-pMG36e-GLP-1, the fasting blood glucose (FPG) of monkeys was significantly (p < 0.05) reduced to a normal level and only a small amount of weight was lost. The results of metagenomic sequencing showed that L. plantarum-pMG36e-GLP-1 caused a substantial (p < 0.05) reduction in the intestinal pathogen Prevotella and marked enhancement of butyrate-producing Alistipes genera. According to the functional analysis using Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways, 19 metabolism-related pathways were significantly enriched in T2DM monkeys after treatment with L. plantarum-pMG36e-GLP-1. LC-MS faecal metabolomics analysis found 41 significant differential metabolites (11 higher and 30 lower) in monkeys after treatment pathways linked to the metabolism of cofactors and vitamins were the most relevant. The present study suggests that L. plantarum-pMG36e-GLP-1 had an impact on the gut microbial composition and faecal metabolomic profile in spontaneous T2DM monkeys and may be a novel candidate for diabetes treatment.

Cardiovascular disease in diabetes, beyond glucose

Despite the decades-old knowledge that diabetes mellitus is a major risk factor for cardiovascular disease, the reasons for this association are only partially understood. While this association is true for both type 1 and type 2 diabetes, different pathophysiological processes may be responsible. Lipids and other risk factors are indeed important, whereas the role of glucose is less clear. This lack of clarity stems from clinical trials that do not unambiguously show that intensive glycemic control reduces cardiovascular events. Animal models have provided mechanisms that link diabetes to increased atherosclerosis, and evidence consistent with the importance of factors beyond hyperglycemia has emerged. We review clinical, pathological, and animal studies exploring the pathogenesis of atherosclerosis in humans living with diabetes and in mouse models of diabetes. An increased effort to identify risk factors beyond glucose is now needed to prevent the increased cardiovascular disease risk associated with diabetes.

Comparison of cine and real-time cardiac MRI in rhesus macaques

Cardiac MRI in rhesus macaques, a species of major relevance for preclinical studies on biological therapies, requires artificial ventilation to realize breath holding. To overcome this limitation of standard cine MRI, the feasibility of Real-Time (RT) cardiac MRI has been tested in a cohort of ten adult rhesus macaques using a clinical MR-system. In spite of lower tissue contrast and sharpness of RT-MRI, cardiac functions were similarly well assessed by RT-MRI compared to cine MRI (similar intra-subject repeatability). However, systematic underestimation of the end-diastolic volume (31 ± 9%), end-systolic volume (20 ± 11%), stroke volume (40 ± 12%) and ejection fraction (13 ± 9%) hamper the comparability of RT-MRI results with those of other cardiac MRI methods. Yet, the underestimations were very consistent (< 5% variability) for repetitive measurements, making RT-MRI an appropriate alternative to cine MRI for longitudinal studies. In addition, RT-MRI enabled the analysis of cardio-respiratory coupling. All functional parameters showed lower values during expiration compared to inspiration, most likely due to the pressure-controlled artificial ventilation. In conclusion, despite systematic underestimation of the functional parameters, RT-MRI allowed the assessment of left ventricular function in macaques with significantly less experimental effort, measurement time, risk and burden for the animals compared to cine MRI.

A Role of Glucose Overload in Diabetic Cardiomyopathy in Nonhuman Primates

Type 2 diabetes (T2D) plays a major role in the development of heart failure. Patients with T2D have an increased risk to develop HF than healthy subjects, and they always have very poor outcomes and survival rates. However, the underlying mechanisms for this are still unclear. To help develop new therapeutic interventions, well-characterized animal models for preclinical and translational investigations in T2D and HF are urgently needed. Although studies in rodents are more often used, the research findings in rodents have often failed to be translated into humans due to the significant metabolic differences between rodents and humans. Nonhuman primates (NHPs) serve as valuable translational models between basic studies in rodent models and clinical studies in humans. NHPs can recapitulate the natural progress of these diseases in humans and study the underlying mechanism due to their genetic similarity and comparable spontaneous T2D rates to humans. In this review, we discuss the importance of using NHPs models in understanding diabetic cardiomyopathy (DCM) in humans with aspects of correlations between hyperglycemia and cardiac dysfunction progression, glucose overload, and altered glucose metabolism promoting cardiac oxidative stress and mitochondria dysfunction, glucose, and its effect on cardiac resynchronization therapy with defibrillator (CRT-d), the currently available diabetic NHPs models and the limitations involved in the use of NHP models.

Cardiac MRI in common marmosets revealing age-dependency of cardiac function

The aim of this study was to establish a feasible and robust magnetic resonance imaging protocol for the quantitative assessment of cardiac function in marmosets and to present normal values of cardiac function across different ages from young adult, middle-aged, to very old clinically healthy animals. Cardiac MRI of 33 anesthetized marmosets at the age of 2-15 years was performed at 9.4 T using IntraGate-FLASH that operates without any ECG-triggering and breath holding. Normalized to post-mortem heart weight, the left ventricular end-diastolic volume (LV-EDV) was significantly reduced in older marmosets. The LV end-systolic volume (LV-ESV) and the LV stroke volume (LV-SV) showed a similar trend while the LV ejection fraction (LV-EF) and wall thickening remained unchanged. Similar observations were made for the right ventricle. Moreover, the total ventricular myocardial volume was lower in older monkeys while no significant difference in heart weight was found. In conclusion, IntraGate-FLASH allowed for quantification of left ventricular cardiac function but seems to underestimate the volumes of the right ventricle. Although less strong and without significant sex differences, the observed age related changes were similar to previously reported findings in humans supporting marmosets as a model system for age related cardiovascular human diseases.

Evaluating the correlation of the impairment between skeletal muscle and heart using MRI in a spontaneous type 2 diabetes mellitus rhesus monkey model

AIMS

To investigate the correlation of impairment in skeletal muscle and heart in spontaneous type 2 diabetes mellitus (T2DM) rhesus monkeys using magnetic resonance image (MRI).

METHODS

Fifteen T2DM monkeys and fourteen healthy control (HC) monkeys were included. The microcirculation of skeletal muscle [skeletal muscle blood flow (SMBF), skeletal muscle oxygen extraction fraction (SMOEF)] and the function and strain of heart were evaluated by MRI. Three regions of interests were chosen on the soleus muscle (SOL), gastrocnemius muscle (GAS) and tibialis anterior muscle (TA) for image analysis.

RESULTS

Eight T2DM monkeys and eight HC monkeys were obtained the full data. The SMBF reserves and SMOEF reserves were found significantly decreased in T2DM during inflation in SOL, GAS and TA muscles (all p < 0.05), and the SMBF reserves decreased during hyperemia in GAS and TA muscles (all p < 0.05). In these monkeys, the global peak longitudinal strain (longitudinal PS), peak systolic longitudinal strain rate (longitudinal PSSR) and peak diastolic longitudinal strain rate (longitudinal PDSR) were seen significantly different in T2DM compared to HC monkeys (all p < 0.05). The longitudinal PSSR was found negatively correlated with SMBF reserves in SOL, GAS and TA during inflation in all monkeys.

CONCLUSIONS

The impaired microcirculation of skeletal muscle and the myocardial deformation were found in T2DM monkeys with normal ejection fraction. And a negative correlation was existed in the longitudinal PSSR and the SMBF reserves.

A rat model of enhanced glycation mimics cardiac phenotypic components of human type 2 diabetes : A translational study using MRI

BACKGROUND

The success of translational research depends on how well animal models mimic the pathophysiology of the human phenotype, and on the identification of disease mechanisms such as enhanced glycation.

METHODS

Here, we studied cardiac MRI and metabolic phenotypes in human type 2 diabetes (N = 106; 55 patients+51 controls) and animal models with distinct levels of fat diet and end glycation products, to model the role of these factors in the cardiac phenotype. We included four groups of rats, designed to evaluate the role of lipid load and glucotoxicity in cardiac function and to correlate these with the cardiac phenotype observed in humans. We also aimed to assess into which extent phenotypes were related to specific risk factors.

RESULTS

Stroke Volume (SV) and Peak Filling Rate (PFR) measures were similarly discriminative both in humans and animal models, particularly when enhanced glycation was present. Factorial analysis showed that reduction of multidimensionality into common main explanatory factors, in humans and animals, revealed components that equally explained the variance of cardiac phenotypes (87.62% and 83.75%, respectively). One of the components included, both in humans and animals, SV, PFR and peak ejection rate (PER). The other components included in both humans and animals are the following: ESV (end systolic volume), left ventricular mass (LVM) and ejection fraction (EF). These components were useful for between group discrimination.

CONCLUSIONS

We conclude that animal models of enhanced glycation and human type 2 diabetes share a striking similarity of cardiac phenotypic components and relation with metabolic changes, independently of fact content in the diet, which reinforces the role of glucose dysmetabolism in left ventricular dysfunction and provides a potentially useful approach for translational research in diabetes, in particular when testing new therapies early on during the natural history of this condition.

Current advances in the study of diabetic cardiomyopathy: From clinicopathological features to molecular therapeutics (Review)

The incidence of diabetes mellitus has become a major public health concern due to lifestyle alterations. Moreover, the complications associated with diabetes mellitus deeply influence the quality of life of patients. Diabetic cardiomyopathy (DC) is a type of diabetes mellitus complication characterized by functional and structural damage in the myocardium but not accompanied by coronary arterial disease. Currently, diagnosing and preventing DC is still a challenge for physicians due to its atypical symptoms. For this reason, it is necessary to summarize the current knowledge on DC, especially in regards to the underlying molecular mechanisms toward the goal of developing useful diagnostic approaches and effective drugs based on these mechanisms. There exist several review articles which have focused on these points, but there still remains a lot to learn from published studies. In this review, the features, diagnosis and molecular mechanisms of DC are reviewed. Furthermore, potential therapeutic and prophylactic drugs are discussed.

mGAP: the macaque genotype and phenotype resource, a framework for accessing and interpreting macaque variant data, and identifying new models of human disease

Background

Non-human primates (NHPs), particularly macaques, serve as critical and highly relevant pre-clinical models of human disease. The similarity in human and macaque natural disease susceptibility, along with parallel genetic risk alleles, underscores the value of macaques in the development of effective treatment strategies. Nonetheless, there are limited genomic resources available to support the exploration and discovery of macaque models of inherited disease. Notably, there are few public databases tailored to searching NHP sequence variants, and no other database making use of centralized variant calling, or providing genotype-level data and predicted pathogenic effects for each variant.

Results

The macaque Genotype And Phenotype (mGAP) resource is the first public website providing searchable, annotated macaque variant data. The mGAP resource includes a catalog of high confidence variants, derived from whole genome sequence (WGS). The current mGAP release at time of publication (1.7) contains 17,087,212 variants based on the sequence analysis of 293 rhesus macaques. A custom pipeline was developed to enable annotation of the macaque variants, leveraging human data sources that include regulatory elements (ENCODE, RegulomeDB), known disease- or phenotype-associated variants (GRASP), predicted impact (SIFT, PolyPhen2), and sequence conservation (Phylop, PhastCons). Currently mGAP includes 2767 variants that are identical to alleles listed in the human ClinVar database, of which 276 variants, spanning 258 genes, are identified as pathogenic. An additional 12,472 variants are predicted as high impact (SnpEff) and 13,129 are predicted as damaging (PolyPhen2). In total, these variants are predicted to be associated with more than 2000 human disease or phenotype entries reported in OMIM (Online Mendelian Inheritance in Man). Importantly, mGAP also provides genotype-level data for all subjects, allowing identification of specific individuals harboring alleles of interest.

Conclusions

The mGAP resource provides variant and genotype data from hundreds of rhesus macaques, processed in a consistent manner across all subjects (https://mgap.ohsu.edu). Together with the extensive variant annotations, mGAP presents unprecedented opportunity to investigate potential genetic associations with currently characterized disease models, and to uncover new macaque models based on parallels with human risk alleles.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5559-7) contains supplementary material, which is available to authorized users.

Region-resolved proteomics profiling of monkey heart

Nonhuman primates (NHPs) play an indispensable role in biomedical research because of their similarities in genetics, physiological, and neurological function to humans. Proteomics profiling of monkey heart could reveal significant cardiac biomarkers and help us to gain a better understanding of the pathogenesis of heart disease. However, the proteomic study of monkey heart is relatively lacking. Here, we performed the proteomics profiling of the normal monkey heart by measuring three major anatomical regions (vessels, valves, and chambers) based on iTRAQ‐coupled LC‐MS/MS analysis. Over 3,200 proteins were identified and quantified from three heart tissue samples. Furthermore, multiple bioinformatics analyses such as gene ontology analysis, protein–protein interaction analysis, and gene‐diseases association were used to investigate biological network of those proteins from each area. More than 60 genes in three heart regions are implicated with heart diseases such as hypertrophic cardiomyopathy, heart failure, and myocardial infarction. These genes associated with heart disease are mainly enriched in citrate cycle, amino acid degradation, and glycolysis pathway. At the anatomical level, the revelation of molecular characteristics of the healthy monkey heart would be an important starting point to investigate heart disease. As a unique resource, this study can serve as a reference map for future in‐depth research on cardiac disease‐related NHP model and novel biomarkers of cardiac injury.

MR extracellular volume mapping and non-contrast T1ρ mapping allow early detection of myocardial fibrosis in diabetic monkeys

Objective

To detect diffuse myocardial fibrosis in different severity levels of left ventricular diastolic dysfunction (DD) in spontaneous type 2 diabetes mellitus (T2DM) rhesus monkeys.

Methods

Eighteen spontaneous T2DM and nine healthy monkeys were studied. Echocardiography was performed for diastolic function classification. Cardiac magnetic resonance (CMR) imaging was performed to obtain extracellular volume fraction (ECV) maps and T1ρ maps at two different spin-locking frequencies. ECV values, T1ρ values, and myocardial fibrosis index (mFI) values which are based on the dispersion of T1ρ, were calculated. Global peak diastolic longitudinal strain rates (GSrL) were also obtained.

Results

Echocardiography results showed mild DD in nine T2DM monkeys and moderate DD in the other nine. The global ECV values were significantly different among healthy animals as compared with animals with mild DD or moderate DD, and the ECV values of animals with moderate DD were significantly higher as compared with those of mild DD. The mFI values increased progressively from healthy animals to those with mild DD and then to those with moderate DD. Diastolic function indicators (e.g., early diastolic mitral annulus velocity, GSrL) correlated well with ECV and mFI.

Conclusions

Monkeys with T2DM exhibit increased ECV, T1ρ, and mFI values, which may be indicative of the expansion of extracellular volume and the deposition of excessive collagen. T1ρ mapping may have the potential to be used for diffuse myocardial fibrosis assessment.

Key Points

• Monkeys with T2DM exhibit increased ECV, T1ρ, and mFI values, which may be indicative of the expansion of extracellular volume and the deposition of excessive collagen.

• The relationship between diastolic dysfunction and diffuse myocardial fibrosis may be demonstrated by imaging markers.

• Non-contrast T1ρ mapping may have the potential to be used for diffuse myocardial assessment.

Electronic supplementary material

The online version of this article (10.1007/s00330-018-5950-9) contains supplementary material, which is available to authorized users.

Plasma lipidomic signatures of spontaneous obese rhesus monkeys

Background

Obesity plays crucial roles in the pathogenesis of metabolic diseases such as hyperlipidemia, nonalcoholic fatty liver disease (NAFLD), and type 2 diabetes (T2D). The underlying mechanisms linking obesity to metabolic diseases are still less understandable.

Methods

Previously, we screened a group of spontaneously obese rhesus monkeys. Here, we performed a plasma lipidomic analysis of normal and obese monkeys using gas chromatography/mass spectroscopy (GC/MS) and ultra-high performance liquid chromatography/mass spectroscopy (UPLC/MS).

Results

In total, 143 lipid species were identified, quantified, and classified into free fatty acids (FFA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylglycerol (PG), lysophosphatidylcholine (LPC), lysophosphatidic acid (LPA), and sphingomyelin (SM). Data analysis showed that the obese monkeys had increased levels of fatty acids palmitoleic acid (C16:1) and arachidonic acid (C20:4), FFA especially palmitic acid (C16:0), as well as certain PC species and SM species. Surprisingly, the plasma level of LPA-C16:0 was approximately four-fold greater in the obese monkeys. Conversely, the levels of most PE species were obviously reduced in the obese monkeys.

Conclusion

Collectively, our work suggests that lipids such as FFA C16:0 and 16:0-LPA may be potential candidates for the diagnosis and study of obesity-related diseases.

2D/3D CMR tissue tracking versus CMR tagging in the assessment of spontaneous T2DM rhesus monkeys with isolated diastolic dysfunction

BACKGROUND

Spontaneous T2DM in rhesus monkeys manifests as isolated diastolic dysfunction in the early stage of diabetic cardiomyopathy, similar to humans. Myocardial deformation measurements have emerged as a superior way to measure left ventricular (LV) function in the early stage of cardiac dysfunction, making it possible to further evaluate early-stage LV dysfunction in spontaneous T2DM rhesus monkeys.

METHODS

Spontaneous T2DM rhesus monkeys with isolated diastolic dysfunction (T2DM-DD, n = 10) and corresponding nondiabetic healthy animals (ND, n = 9) were prospectively scanned for a CMR study. Circumferential and longitudinal peak systolic strain (Ecc, Ell), time to peak strain (tEcc, tEll) and peak diastolic strain rate (CSR, LSR) obtained from 2D/3D CMR-TT were compared with those obtained from CMR tagging separately. In addition, all CMR imaging protocols were performed twice in 9 ND animals to assess test-retest reproducibility.

RESULTS

Compared with the ND group, the T2DM-DD monkeys demonstrated significantly impaired LV Ecc (- 10.63 ± 3.23 vs - 14.18 ± 3.19, p < 0.05), CSR (65.50 ± 14.48 vs 65.50 ± 14.48, p < 0.01), Ell (- 9.11 ± 2.59 vs - 14.17 ± 1.68, p < 0.05), and LSR (59.43 ± 19.17 vs 108.46 ± 22.33, p < 0.01) with the tagging. Only Ecc (- 13.10 ± 2.47 vs - 19.03 ± 3.69, p < 0.01) and CSR (148.90 ± 31.27 vs 202.00 ± 51.88, p < 0.01) were significantly reduced with 2D CMR-TT, and only Ecc (- 13.77 ± 1.98 vs - 17.26 ± 3.78, p < 0.05) was significantly reduced with 3D CMR-TT. Moreover, 2D/3D CMR-TT-derived Ecc and CSR correlated with the corresponding tagging values collectively, with a statistically significant ICC value (p < 0.05). Test-retest repeatability analysis showed that most tagging-derived biomarkers had acceptable repeatability (p < 0.01). In addition, 2D CMR-TT-derived indicators were poorer than those derived from the tagging method but better than those obtained using the 3D method, with larger ICCs except for tEcc (p < 0.05).

CONCLUSIONS

LV systolic and diastolic deformations were impaired in spontaneous T2DM rhesus monkeys previously diagnosed with isolated diastolic dysfunction by echocardiography. The 2D CMR-TT-derived Ecc and CSR were effective in the evaluation of the myocardial systolic and diastolic functions of early-diabetic cardiomyopathy, with relatively higher test-retest reproducibility and acceptable correlation with the tagging method compared with the 3D CMR-TT method.

SILAC-based quantitative proteomic analysis of the livers of spontaneous obese and diabetic rhesus monkeys

Type 2 diabetes mellitus (T2DM) is a severe metabolic disorder that affects more than 10% of the population worldwide. Obesity is a major cause of insulin resistance and contributes to the development of T2DM. Liver is an essential metabolic organ that plays crucial roles in the pathogenesis of obesity and diabetes. However, the underlying mechanisms of liver in the transition of obesity to diabetes are not fully understood. The nonhuman primate rhesus monkey is an appropriate animal for research of human diseases. Here, we first screened and selected three individuals of spontaneously diabetic rhesus monkeys. Interestingly, the diabetic monkeys were obese with a high body mass index at the beginning, but gradually lost their body weight during one year of observation. Furthermore, we performed stable isotope labeling with amino acids in cell culture-based quantitative proteomics to identify proteins and signaling pathways with altered expression in the liver of obese and diabetic monkeys. In total, 3,509 proteins were identified and quantified, of which 185 proteins displayed an altered expression level. Gene ontology analysis revealed that the expression of proteins involved in fatty acids β-oxidation and galactose metabolism was increased in obese monkeys; while proteins involved in oxidative phosphorylation and branched chain amino acid (BCAA) degradation were upregulated in diabetic monkeys. In addition, we observed mild apoptosis in the liver of diabetic monkeys, suggesting liver injury at the late onset of diabetes. Taken together, our liver proteomics may reveal a distinct metabolic transition from fatty acids β-oxidation in obese monkey to BCAA degradation in diabetic monkeys.

Morphometric and morphologic parameters of the heart in healthy Alouatta guariba clamitans (Cabrera, 1940)

BACKGROUND

This study aimed at assessing the heart function of one neotropical primate (Alouatta guariba clamitans) kept in captivity using radiography, electrocardiogram (ECG) and Doppler echocardiography.

METHODS

Ten adult healthy howler monkeys (A. g. clamitans) were evaluated under general anaesthesia. Vertebral Heart Scores (VHS) were obtained from radiographic studies. Ejection fraction, shortening fraction of left ventricle, left atrial/aortic root ratio, ascending aortic diameter, peak velocity of pulmonary, mitral, tricuspid and aortic blood flow and other values were measured by Doppler echocardiography. Heart rate, mean electrical axis of QRS complex, P, Q, R, S, T amplitude, P, PR interval, QRS, QT interval duration and ST segment unbalancing were measured by ECG.

RESULTS AND CONCLUSIONS

Exam techniques were akin the ones used in humans. Doppler echocardiographic, radiographic, electrocardiographic and clinical parameters for howler monkey were described and correlated. The results have shown profiles of cardiovascular function and structure of A. g. clamitans.

Echocardiographic Parameters of Clinically Normal Geriatric Rhesus Macaques (Macacamulatta)

The goal of this study was to generate reference intervals for echocardiographic variables in a population of clinically normal geriatric rhesus macaques (Macaca mulatta). To do this, we studied 51 animals (age, 18-29 y; weight, 5.24-17.04 kg). The normal values for cardiac indices, including geometry and systolic and diastolic function, were determined by 2D, M-mode, spectral Doppler, and tissue Doppler echocardiography under ketamine hydrochloride sedation. Statistical correlations between the echocardiographic parameters and age, body weight, sex, and heart rate were investigated. All echocardiographic indices were acquired, and their reference intervals were established. Multiple weak to strong correlations emerged between variables and echocardiographic parameters, but no moderate or strong correlations between body weight or sex and these parameters were noted. Of the 51 geriatric rhesus macaques evaluated, 36 (71%) fulfilled the criteria for diastolic dysfunction. Valve regurgitation, especially tricuspid regurgitation (43%), and aortic regurgitation (51%) also were common in geriatric rhesus macaques. Although these findings merit follow-up, they are unlikely to have clinical significance given their prevalence in these apparently healthy animals.

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.

Quantitative MRI biomarkers to characterize regional left ventricular perfusion and function in nonhuman primates during dobutamine-induced stress: A reproducibility and reliability study

PURPOSE

To identify reproducible and reliable noninvasive regional imaging biomarkers of cardiac function and perfusion at rest and under stress in healthy nonhuman primates (NHPs) that may be used in the future for the early characterization of preclinical heart failure models, to evaluate therapy, and for clinical translation.

MATERIALS AND METHODS

Seven naive cynomolgus macaques underwent test-retest 3T cardiac MRI tagging and dual-bolus perfusion experiments. Regional cardiac function biomarkers, such as peak circumferential strain (CS), average diastolic strain-rate (DSR), contractile reserve (CR), diastolic reserve, peak torsion, and torsion reserve were quantified. Further, regional myocardial blood flow (MBF), myocardial perfusion reserve (MPR), and myocardial perfusion reserve-to-contractile reserve (MPR/CR) were also derived. Inter- and intraobserver reproducibility and test-retest reliability analyses were conducted using the reliability and generalizability coefficients including correlation coefficient (CC) and intraclass correlation coefficient (ICC).

RESULTS

Overall, peak CS, DSR, and MBF are robust biomarkers at both rest and stress with moderate-good inter- and intraobserver reproducibility and test-retest reliability. At rest: intra-/interobserver reproducibility (CC): peak CS (0.81/0.81), DSR (0.81/0.81), MBF (0.72/0.57), peak torsion (0.79/0.79); test-retest reliability: (CC/ICC): peak CS (0.62/0.75), DSR (0.24/0.55), MBF (0.66/0.62), and peak torsion (0.79/0.78). Under stress: intra-/interobserver reproducibility (CC): peak CS (0.61/0.60), DSR (0.50/0.50), MBF (0.63/0.61), MPR (0.43/0.43), and peak torsion (0.38/0.38); test-retest reliability: (CC/ICC): peak CS (0.58/0.58), DSR (0.24/0.43), MBF (0.58/0.58), MPR (0.43/0.38), and peak torsion (0.38/0.38).

CONCLUSION

We demonstrated the feasibility of using cardiac MRI to characterize left ventricular functional and perfusion responses to stress in an NHP species, and specific robust biomarkers such as peak CS, DSR, MBF, diastolic reserve, and MPR have been identified for clinical translation and drug research.

LEVEL OF EVIDENCE

1 J. Magn. Reson. Imaging 2017;45:556-569.

Animal models of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) constitutes a clinical syndrome in which the diagnostic criteria of heart failure are not accompanied by gross disturbances of systolic function, as assessed by ejection fraction. In turn, under most circumstances, diastolic function is impaired. Although it now represents over 50 % of all patients with heart failure, the mechanisms of HFpEF remain understood, precluding effective therapy. Understanding the pathophysiology of HFpEF has been restricted by both limited access to human myocardial biopsies and by the lack of animal models that fully mimic human pathology. Animal models are valuable research tools to clarify subcellular and molecular mechanisms under conditions where the comorbidities and other confounding factors can be precisely controlled. Although most of the heart failure animal models currently available represent heart failure with reduced ejection fraction, several HFpEF animal models have been proposed. However, few of these fulfil all the features present in human disease. In this review we will provide an overview of the currently available models to study HFpEF from rodents to large animals as well as present advantages and disadvantages of these models.