Jingqiu Cheng

Regulation of SIRT1 in aging: Roles in mitochondrial function and biogenesis

Aging is a degenerative process associated with cumulative damage, which leads to cellular dysfunction, tissue failure, and disorders of body function. Silent information regulator-1, also known as sirtuin 1 (SIRT1), has been reported to be involved in the regulation of various important biological processes, including inflammation, mitochondrial biogenesis, as well as cell senescence and consequent aging. The level of SIRT1 is decreased in both transcriptional and postranscriptional conditions during aging, accompanied by attenuated mitochondrial biogenesis, an important component of aging-related diseases. Over the last decade, extensive studies have demonstrated that SIRT1 can activate several transcriptional factors, such as peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α) and hypoxia-inducible factor 1α (HIF-1α) resulting in ameliorated mitochondria biogenesis and extended life span. In this review, we focus on the molecular regulation of SIRT1 and its role in mitochondrial biogenesis during in the context of aging and aging-related diseases.

Induction of Diabetes in Rhesus Monkeys and Establishment of Insulin Administration Strategy

OBJECTIVES The diabetic rhesus monkey seems to be a useful model for preclinical investigations of islet transplantation and new drug treatments for type 1 diabetes mellitus (T1DM). Information is limited regarding a standard technique to induce and assess diabetes in rhesus monkeys as well as the strategy to apply insulin administration. Herein, we have established and characterized a model of diabetic rhesus macaques. METHODS Four monkeys were divided into 2 groups of 2 each: group 1, total pancreatectomy; and group 2, partial pancreatectomy (75%) with low-dose streptozotocin (STZ) administration. Pancreatic function was measured using intravenous glucose tolerance tests before the operation. Spiral computed tomography (CT) scans of the pancreas were obtained before and after pancreatectomy. Fasting blood glucose and postprandial blood glucose levels were monitored twice daily using blood samples from the fingers or toes. Various types and doses of insulin were administered twice daily. We performed regular assessments of hematological and serum biochemical parameters, insulin, and C-peptide. RESULTS Both total pancreatectomy and partial pancreatectomy (75%) with STZ administration induced T1DM in rhesus monkeys; there was interindividual variation in the STZ dose. Excluding C-peptide and insulin, the hematological and serum biochemical parameters did not differ significantly from normal values postoperatively. The various insulin treatment strategies are achieved stable blood glucose (BG) levels. CONCLUSIONS STZ injection after partial pancreatectomy may be a safe, reproducible method to induce T1DM. Porcine insulin administration was a safe, economical method to control BG levels in a diabetic rhesus monkey before islet transplantation.

A Preliminary Study on the Feasibility of Gene Expression Profile of Rhesus Monkey Detected With Human Microarray

OBJECTIVES A pig-to-monkey transplant model was initiated to investigate the outcome of pig-to-human xenotransplantation. Though monkey is close to human in biology and physiology, the genetic differences between the two species remains unclear. This study sought to compare the gene expressions of three tissues from humans and rhesus monkey. METHODS RNA samples extracted from liver, spleen, and peripheral blood cells were hybridized onto Illumina gene expression microarray. Genes with detected signals greater than 1000 and diff-scores higher than 100 were selected as significant results. The data were analyzed with Illumina software. mRNA expression levels were confirmed by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis. RESULTS Of the 47,293 transcripts tested on every gene chip, more than 6000 genes were expressed in three tissues. Total numbers of genes detected and the similarity ratios followed the same rule as liver < PBC < spleen. The 136 IRI-related genes, 192 immunological-related genes, and 131 cell cycle-related genes selected and analyzed showed gene expression concordance rates of 82.35%, 72.92%, and 77.10%, respectively. RT-PCR tests indicated similar mRNA expression levels of RTN4, interleukin (IL)-1beta, NF-kappaB1, IL-8, and G0S2 to the results on chips. CONCLUSIONS The detected mRNA expressions in human and monkey tissues showed an average consistency in 85.78%, indicating that a human microarray might provide a part of the information for monkey sample testing. Therefore, in pig-to-monkey transplant models, monkey microarray may be used to determine recipient gene expressions. The genetic difference between human and monkey must be taken into account in interpreting the experimental results.

Induction of diabetes with signs of autoimmunity in primates by the injection of multiple-low-dose streptozotocin

AIM To develop a preclinical large animal model of autoimmune diabetes to facilitate the translational research of autoimmune diabetes in human. MATERIALS AND METHODS Nine young rhesus monkeys received multiple-low-dose (MLD) intravenous injections of streptozotocin for five consecutive days, followed by two additional boosting injections of STZ given 1 week apart. The induction of autoimmune diabetes was evaluated by regular metabolic testing, serological assessment of islet-reactive autoantibodies and histological examination of pancreatic tissues. RESULTS Seven of nine treated animals became diabetic with moderate hyperglycemia initially and more severe hyperglycemia thereafter. All diabetic animals exhibited severely impaired glucose tolerance, limited islet function, and required insulin therapy to maintain relatively normal glucose metabolism and healthy status. Serological tests showed that all diabetic monkeys developed autoantibodies specifically against insulin and islet antigens. Furthermore, histological examination of the pancreata from diabetic animals revealed evidence of specific destruction of islet β cells and islets infiltrated with T lymphocytes. Overt and persistent diabetes can be induced in young rhesus monkeys by the injection of MLD-STZ, and autoimmune responses to pancreatic islet cells seem to be involved in the development of glucose intolerance and diabetes. CONCLUSION These data indicate for the first time that autoimmune diabetes can be induced in primates; this may serve as a valuable preclinical model for studying the pathogenesis of and potential therapies for autoimmune diabetes in humans.

Self-Assembling Peptide Nanofiber as Potential Substrates in Islet Transplantation

Hypoxia and reoxygenation (H/R)-induced damage often happens soon after islets are transplantation. The process of islet isolation and purification causes the rapid onset of hypoxia. We sought to develop a functional scaffold to sustain the structure and function of islets as well as to recover some of the surface molecules damaged during isolation, seeking to improve islet transplantation outcomes. Self-assembling peptide nanofiber (SAPNF), a new type of substrate has been shown to be an excellent biological material for neuronal cell culture and tissue engineering in animals. In this study, we investigated the protective effect of SAPNF on damage to rat islets. Freshly prepared rat islets from male Sprague-Dawley rats were seeded in plates coated with (SAPNF-treated group) or without (control group) SAPNF. The islets were then divided into two groups culture under normoxia for 7 days versus exposure to hypoxia (< 1% O2) for 6 hours followed by reoxygenation for 24 hours. The results showed that SAPNF exhibited improving effects on viability and function of cultured islets, protecting the one from H/R-induced damage. In both groups, the stimulation index of SAPNF-treated groups were about two times the controls. SAPNF treatment decreased apoptotic rates of islet cells. These results suggested the usefulness of SAPNF to maintain the viability and function of rat pancreatic islets. SAPNF may be a potential scaffold for clinical islet transplantation.

DPP IV inhibitor suppresses STZ-induced islets injury dependent on activation of the IGFR/Akt/mTOR signaling pathways by GLP-1 in monkeys

BACKGROUND To evaluate the protective effect of the DPP IV inhibitor in STZ-induced islet injury and to identify the molecular events that protect islet against apoptosis. METHODS 4 diabetic monkeys were treated with streptozotocin (70 mg/kg) in the presence or absence of the DPP IV inhibitor (Sitagliptin), continuing administered for 4 weeks after STZ. The monkeys were evaluated by plasma DPP IV activity, serum active GLP-1 response, blood glucose, insulin and C-P levels, the insulin resistance index (HOMA-IR), and the expression of insulin, caspase-3, IGF receptor (IGFR), p-Akt and p-mTOR in pancreas islets tissues. To test that DPP IV inhibitors might against islets apoptosis via IGFR/Akt/mTOR signaling pathways, the isolated islets from the normal monkeys were pre-treated with or without 10mM STZ for 1h, followed by GLP-1 (10 μM) in the presence or absence of NVP-AEW541 or Wortmannin for 24h, to determined islets function and islet apoptosis. RESULTS DPP IV inhibitors treatment showed depressing the degradation of GLP-1 and significantly increased serum GLP-1 levels in DM monkeys. Moreover, treatment of diabetic monkeys with the DPP IV inhibitor or treatment of isolated islets with GLP-1 can decrease islet apoptosis, and enhanced islet function and survival, and the expression of IGF receptor, p-Akt and p-mTOR in islets. When the IGFR/Akt/mTOR signaling pathways was blocked by NVP-AEW541 or Wortmannin, the protective effects of GLP1 on STZ-induced islets injury were inhibited in vitro. CONCLUSIONS Our data provides evidence that DPP IV inhibitors confer resistance to STZ-induced islet injury. The protective effects of DPP IV inhibitor on STZ-induced islets injury were dependent on activation of the IGFR/Akt/mTOR signaling pathways by GLP-1 in islets of monkeys.

Exacerbation of Glycoprotein VI-Dependent Platelet Responses in a Rhesus Monkey Model of Type 1 Diabetes

Thrombosis is a life-threatening complication of diabetes. Platelet reactivity is crucial to thrombus formation, particularly in arterial vessels and in thrombotic complications causing myocardial infarction or ischaemic stroke, but diabetic patients often respond poorly to current antiplatelet medication. In this study, we used a nonhuman primate model of Type 1 diabetes to measure early downstream signalling events following engagement of the major platelet collagen receptor, glycoprotein (GP)VI. Diabetic monkeys were given enough insulin to maintain their blood glucose levels either at ~8 mM (well-controlled diabetes) or ~15 mM (poorly controlled diabetes). Flow cytometric analysis was used to measure platelet reactive oxygen species (ROS) generation, calcium mobilisation, receptor surface expression, and immature platelet fraction. We observed exacerbated intracellular ROS and calcium flux associated with engagement of GPVI in monkeys with poorly controlled diabetes. GPVI surface levels did not differ between healthy monkeys or the two diabetic groups. Treatment of platelets with the specific Syk inhibitor BAY61-3606 inhibited GPVI-dependent ROS and, importantly, reduced ROS generation in the poorly controlled diabetes group to that observed in healthy monkeys. These data indicate that glycaemic control is important in reducing GPVI-dependent platelet hyperreactivity and point to a potential antithrombotic therapeutic benefit of Syk inhibition in hyperglycaemic diabetes.

A preclinical evaluation of alternative site for islet allotransplantation

The bone marrow cavity (BMC) has recently been identified as an alternative site to the liver for islet transplantation. This study aimed to compare the BMC with the liver as an islet allotransplantation site in diabetic monkeys. Diabetes was induced in Rhesus monkeys using streptozocin, and the monkeys were then divided into the following three groups: Group1 (islets transplanted in the liver with immunosuppressant), Group 2 (islets transplanted in the tibial BMC), and Group 3 (islets transplanted in the tibial BMC with immunosuppressant). The C-peptide and blood glucose levels were preoperatively measured. An intravenous glucose tolerance test (IVGTT) was conducted to assess graft function, and complete blood cell counts were performed to assess cell population changes. Cytokine expression was measured using an enzyme-linked immune sorbent assay (ELISA) and MILLIPLEX. Five monkeys in Group 3 exhibited a significantly increased insulin-independent time compared with the other groups (Group 1: 78.2 ± 19.0 days; Group 2: 58.8 ± 17.0 days; Group 3: 189.6 ± 26.2 days) and demonstrated increases in plasma C-peptide 4 months after transplantation. The infusion procedure was not associated with adverse effects. Functional islets in the BMC were observed 225 days after transplantation using the dithizone (DTZ) and insulin/glucagon stains. Our results showed that allogeneic islets transplanted in the BMC of diabetic Rhesus monkeys remained alive and functional for a longer time than those transplanted in the liver. This study was the first successful demonstration of allogeneic islet engraftment in the BMC of non-human primates (NHPs).

Pancreas anatomy and surgical procedure for pancreatectomy in rhesus monkeys

Background  The aim of this study was to investigate the pancreas anatomy and surgical procedure for harvesting pancreas for islet isolation while performing pancreatectomy to induce diabetes in rhesus monkeys.

Glucocorticoid treatment facilitates development of a metabolic syndrome in ovariectomized Macaca Mulatta fed a high fat diet

HighlightsWe reported for the first time that the endocrine and physiological changes in response to chronic and high dose of GCs in non‐human primates, and the effects of withdrawal of a long‐term treatment, which led to recovery from metabolic disorders.We used ovariectomized monkeys to mimic the situation of perimenopausal and postmenopausal women, and might be used as potential models of Cushing’s syndrome or MetS in non‐human primates.The lipid and glucose related factors including leptin and GLUT4 play important roles in the GCs effect. Abstract Metabolic syndrome (MetS) is characterized by a cluster of key features, which include abdominal obesity, insulin resistance, hypertension, and dyslipidemia. The aim of this study was to assess the impact of elevated glucocorticoid levels on the development of MetS in middle‐aged female rhesus monkeys (Macaca Mulatta) after ovariectomy. Six female ovariectomized rhesus monkeys (9–13 years) were randomly assigned to either a control group (normal diet, n = 3) or a group in which MetS was facilitated (n = 3). The MetS group fed with HFD (15% fat) and received oral prednisone acetate treatment (50 mg/day). After 24 months, the GCs treatment was withdrawn with continuation of high‐fat feeding for a further 12 months. After 24 months, the MetS group displayed a significant increase in body weight and abdominal circumference. Additionally, the MetS animals displayed abnormal serum lipids, insulin resistance and impaired glucose tolerance. Histology of liver biopsies indicated marked accumulation of lipid droplets in hepatocytes of MetS animals. Withdrawal of GCs treatment led to recovery from above‐mentioned metabolic disorders. Whereas GCs treatment increased leptin expression, it lowered expression of adiponectin and other factors in adipose tissue. Expression of Hydroxy‐steroid dehydrogenase‐1 and glucose transporter type‐4 in the livers of MetS animals were reduced. We conclude that in the context of high fat diet, high levels of exogenous GCs contribute to the development of MetS in non‐human primates.