The effect of low versus high dose of streptozotocin in cynomolgus monkeys (Macaca fascilularis)

Amelioration of Murine Diabetic Nephropathy with a SGLT2 Inhibitor Is Associated with Suppressing Abnormal Expression of Hypoxia-Inducible Factors

Diabetic nephropathy (DN), once manifested, is unlikely to completely recover. Factors that influence DN progression were explored by investigating the process of glomerulosclerosis and interstitial fibrosis and chronological changes in glucose, albuminuria, hyperfiltration, and expressions of sodium-glucose cotransporter 2 (SGLT2) and hypoxia-inducible factors (HIFs) up to 50 weeks in inducible cAMP early repressor transgenic mice, a model of severe DN. Long-term intervention with the SGLT2 inhibitor canagliflozin or islet transplantation or heminephrectomy was used. Inducible cAMP early repressor transgenic mice exhibited progressive diabetic glomerulosclerosis and mild interstitial fibrosis, and expressed extensive HIF-1α and HIF-2α in glomerulus and tubules, with sustained hyperfiltration up to 50 weeks. Canagliflozin ameliorated glomerulosclerosis/interstitial fibrosis gradually and reduced HIF overexpression. Islet-transplanted mice exhibited no amelioration. None of the heminephrectomized diabetic mice survived the hyperfiltration overload, but all of the canagliflozin-treated mice survived with re-expressions of HIF-1α and HIF-2α. These results suggest that persistent glomerular hyperfiltration might initiate glomerular injury, and persistent overexpression of HIFs could promote the development of glomerulosclerosis and interstitial fibrosis. Canagliflozin attenuated both changes. Oxidative stress or hypoxia was undetectable in this model. The abnormal expression of HIF-1α and HIF-2α may be a potential therapeutic target for preventing glomerulosclerosis and interstitial fibrosis.

Human pluripotent stem-cell-derived islets ameliorate diabetes in non-human primates

Human pluripotent stem-cell-derived islets (hPSC-islets) are a promising cell resource for diabetes treatment^1,2. However, this therapeutic strategy has not been systematically assessed in large animal models physiologically similar to humans, such as non-human primates³. In this study, we generated islets from human chemically induced pluripotent stem cells (hCiPSC-islets) and show that a one-dose intraportal infusion of hCiPSC-islets into diabetic non-human primates effectively restored endogenous insulin secretion and improved glycemic control. Fasting and average pre-prandial blood glucose levels significantly decreased in all recipients, accompanied by meal or glucose-responsive C-peptide release and overall increase in body weight. Notably, in the four long-term follow-up macaques, average hemoglobin A1c dropped by over 2% compared with peak values, whereas the average exogenous insulin requirement reduced by 49% 15 weeks after transplantation. Collectively, our findings show the feasibility of hPSC-islets for diabetic treatment in a preclinical context, marking a substantial step forward in clinical translation of hPSC-islets.

SUMOylation of Enzymes and Ion Channels in Sensory Neurons Protects against Metabolic Dysfunction, Neuropathy, and Sensory Loss in Diabetes

Diabetic peripheral neuropathy (DPN) is a highly frequent and debilitating clinical complication of diabetes that lacks therapies. Cellular oxidative stress regulates post-translational modifications, including SUMOylation. Here, using unbiased screens, we identified key enzymes in metabolic pathways and ion channels as novel molecular targets of SUMOylation that critically regulated their activity. Sensory neurons of diabetic patients and diabetic mice demonstrated changes in the SUMOylation status of metabolic enzymes and ion channels. In support of this, profound metabolic dysfunction, accelerated neuropathology, and sensory loss were observed in diabetic gene-targeted mice selectively lacking the ability to SUMOylate proteins in peripheral sensory neurons. TRPV1 function was impaired by diabetes-induced de-SUMOylation as well as by metabolic imbalance elicited by de-SUMOylation of metabolic enzymes, facilitating diabetic sensory loss. Our results unexpectedly uncover an endogenous post-translational mechanism regulating diabetic neuropathy in patients and mouse models that protects against metabolic dysfunction, nerve damage, and altered sensory perception.

Induction of diabetes in cynomolgus monkey with one shot of analytical grade streptozotocin

BACKGROUNDS

Streptozotocin (STZ)- induced diabetic monkey is a wide used preclinical animal model for the investigation of diabetes such as islet transplantation and development of diabetic drugs. There are serious side effects of this method, including nausea, emesis, weight loss, liver damage, renal failure, and metabolic acidosis. In order to reduce the side effects, diabetic monkeys were induced using clinical-grade STZ. However, clinical-grade STZ is not available in China. Here, we establised a method by using 100 mg/kg analytical-grade STZ to induce complete diabetes in cynomolgus monkey without generating adverse effects to liver and renal.

METHODS

Three cynomolgus monkeys were used in this study. 100 mg/kg STZ dissolved in normal saline and infused through vein line in 5 minutes after indwelling catheter in the carotid artery and jugular vein. After the STZ administration, blood glucose levels were examined every 1 or 2 hours in the first 48 hours. Then, blood glucose levels were examined twice per day during the first week after the STZ injection. Insulin and C-peptide levels were measured by ELISA. Blood chemistry of hepatic and renal function tests were performed. Insulin and glucagon expression in the islet of diabetic monkey and normal monkey were examined by immunohistochemistry assays.

RESULTS

The stimulated C-peptide level (Intravenous glucose tolerance test) which is less than 0.5 ng/mL, the triphasic blood glucose response and the destroyed β cell suggested the complete induction of diabetes model. No apparent adverse effects were observed including no signs of vomiting and toxicity after STZ injection.

CONCLUSION

In summary, we established a safe and reproducible STZ-induced diabetic cynomolgus monkey model for islet transplantation which will be used to develop novel approaches for the treatment of diabetes.

The 20-Year Voyage Aboard the Journal of Alzheimer's Disease: Docking at 'Type 3 Diabetes', Environmental/Exposure Factors, Pathogenic Mechanisms, and Potential Treatments

The Journal of Alzheimer’s Disease (JAD), founded in 1998, played a pivotal role in broadening the field of research on Alzheimer’s disease (AD) by publishing a diverse range of clinical, pathological, molecular, biochemical, epidemiological, experimental, and review articles from its birth. This article recounts my own journey as an author who contributed articles to JAD over the 20 years of the journal’s existence. In retrospect, it seems remarkable that a considerable body of work that originated from our group marks a trail that began with studies of vascular, stress, and mitochondrial factors in AD pathogenesis, exploded into the concept of ‘Type 3 Diabetes’, and continued with the characterization of how environmental, exposure, and lifestyle factors promote neurodegeneration and which therapeutic strategies could reverse the neurodegeneration cascade.

Metabolomic signature of type 1 diabetes-induced sensory loss and nerve damage in diabetic neuropathy

Diabetic-induced peripheral neuropathy (DPN) is a highly complex and frequent diabetic late complication, which is manifested by prolonged hyperglycemia. However, the molecular mechanisms underlying the pathophysiology of nerve damage and sensory loss remain largely unclear. Recently, alteration in metabolic flux has gained attention as a basis for organ damage in diabetes; however, peripheral sensory neurons have not been adequately analyzed with respect to metabolic dysfunction. In the present study, we attempted to delineate the sequence of event occurring in alteration of metabolic pathways in relation to nerve damage and sensory loss. C57Bl6/j wild-type mice were analyzed longitudinally up to 22 weeks in the streptozotocin (STZ) model of type 1 diabetes. The progression of DPN was investigated by behavioral measurements of sensitivity to thermal and mechanical stimuli and quantitative morphological assessment of intraepidermal nerve fiber density. We employed a mass spectrometry-based screen to address alterations in levels of metabolites in peripheral sciatic nerve and amino acids in serum over several months post-STZ administration to elucidate metabolic dysfunction longitudinally in relation to sensory dysfunction. Although hyperglycemia and body weight changes occurred early, sensory loss and reduced intraepithelial branching of nociceptive nerves were only evident at 22 weeks post-STZ. The longitudinal metabolites screen in peripheral nerves demonstrated that compared with buffer-injected age-matched control mice, mice at 12 and 22 weeks post-STZ showed an early impairment the tricaoboxylic acid (TCA cycle), which is the main pathway of carbohydrate metabolism leading to energy generation. We found that levels of citric acid, ketoglutaric acid (2 KG), succinic acid, fumaric acid, and malic acid were observed to be significantly reduced in sciatic nerve at 22 weeks post-STZ. In addition, we also found the increase in levels of sorbitol and L-lactate in peripheral nerve from 12 weeks post-STZ injection. Amino acid screen in serum showed that the amino acids valine (Val), isoleucine (Ile), and leucine (Leu), grouped together as BCAA, increased more than twofold from 12 weeks post-STZ. Similarly, the levels of tyrosine (Tyr), asparagine (Asn), serine (Ser), histidine (His), alanine (Ala), and proline (Pro) showed progressive increase with progression of diabetes. Our results indicate that the impaired TCA cycle metabolites in peripheral nerve are the primary cause of shunting metabolic substrate to compensatory pathways, which leads to sensory nerve fiber loss in skin and contribute to onset and progression of peripheral neuropathy.

Evoked hypoalgesia is accompanied by tonic pain and immune cell infiltration in the dorsal root ganglia at late stages of diabetic neuropathy in mice

Diabetic peripheral neuropathy is a major debilitating late complication of diabetes, which significantly reduces the quality of life in patients. Diabetic peripheral neuropathy is associated with a wide spectrum of sensory abnormalities, where in loss of sensation or hypoalgesia to applied external stimuli is paradoxically accompanied by debilitating tonic spontaneous pain. In numerous studies on animal models of diabetic peripheral neuropathy, behavioural measurements have been largely confined to analysis of evoked withdrawal to mechanical and thermal stimuli applied to dermatomes, whereas spontaneous, on-going pain has not been widely studied. In the Streptozotocin model of type 1 diabetes, we employed the Conditioned Place Preference test to assess tonic pain. Our results indicate that both phases, that is, early evoked hypersensitivity (i.e. 5–7 weeks post-Streptozotocin) as well as late stage hypoalgesia (i.e. 17–20 weeks post-Streptozotocin) are accompanied by significant tonic pain in mice with diabetic peripheral neuropathy. We also report on the temporal relation between on-going pain and neuropathological changes in the dorsal root ganglia of mice with diabetic peripheral neuropathy up to 6 months post-Streptozotocin. Neither early hypersensitivity nor late hypoalgesia were associated with markers of cellular stress in the dorsal root ganglia. Whereas significant neutrophil infiltration was observed in the dorsal root ganglia over both early and late stages post-Streptozotocin, T-cell infiltration in the dorsal root ganglia was prominent at late stages post-Streptozotocin. Thus, longitudinal analyses reveal that similar to patients with chronic diabetic peripheral neuropathy, mice show tonic pain despite sensory loss after several months in the Streptozotocin model, which is accompanied by neuroimmune interactions in the dorsal root ganglia.

Hypoxia-inducible factor 1α protects peripheral sensory neurons from diabetic peripheral neuropathy by suppressing accumulation of reactive oxygen species

Diabetic peripheral neuropathy (DPN) is one of the most common diabetic complications. Mechanisms underlying nerve damage and sensory loss following metabolic dysfunction remain largely unclear. Recently, hyperglycemia-induced mitochondrial dysfunction and the generation of reactive oxygen species (ROS) have gained attention as possible mechanisms of organ damage in diabetes. Hypoxia-inducible factor 1 (HIF1α) is a key transcription factor activated by hypoxia, hyperglycemia, nitric oxide as well as ROS, suggesting a fundamental role in DPN susceptibility. We analyzed regulation of HIF1α in response to prolonged hyperglycemia. Genetically modified mutant mice, which conditionally lack HIF1α in peripheral sensory neurons (SNS-HIF1α^-/-), were analyzed longitudinally up to 6 months in the streptozotocin (STZ) model of type1 diabetes. Behavioral measurements of sensitivity to thermal and mechanical stimuli, quantitative morphological analyses of intraepidermal nerve fiber density, measurements of ROS, ROS-induced cyclic GMP-dependent protein kinase 1α (PKG1α), and levels of vascular endothelial growth factor (VEGF) in sensory neurons in vivo were undertaken over several months post-STZ injections to delineate the role of HIF1α in DPN. Longitudinal behavioral and morphological analyses at 5, 13, and 24 weeks post-STZ treatment revealed that SNS-HIF1α^-/- developed stronger hyperglycemia-evoked losses of peripheral nociceptive sensory axons associated with stronger losses of mechano- and heat sensation with a faster onset than HIF1α^fl/fl mice. Mechanistically, these histomorphologic, behavioral, and biochemical differences were associated with a significantly higher level of STZ-induced production of ROS and ROS-induced PKG1α dimerization in sensory neurons of SNS-HIF1α^-/- mice as compared with HIF1α^fl/fl. We found that prolonged hyperglycemia induced VEGF expression in the sciatic nerve which is impaired in SNS-HIF1α mice. Our results indicate that HIF1α is as an upstream modulator of ROS in peripheral sensory neurons and exerts a protective function in suppressing hyperglycemia-induced nerve damage by limiting ROS levels and by inducing expression of VEGF which may promote peripheral nerve survival. Our data suggested that HIF1α stabilization may be thus a new strategy target for limiting sensory loss, a debilitating late complication of diabetes. KEY MESSAGES: • Impaired hypoxia-inducible factor 1α (HIF1α) signaling leads to early onset of STZ-induced loss of sensation in mice. • STZ-induced loss of sensation in HIF1α mutant mice is associated with loss of sensory nerve fiber in skin. • Activation of HIF1α signaling in diabetic mice protects the sensory neurons by limiting ROS formation generated due to mitochondrial dysfunction and by inducing VEGF expression.

Improved Brain Insulin/IGF Signaling and Reduced Neuroinflammation with T3D-959 in an Experimental Model of Sporadic Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is associated with progressive impairments in brain insulin, insulin-like growth factor (IGF), and insulin receptor substrate (IRS) signaling through Akt pathways that regulate neuronal growth, survival, metabolism, and plasticity. The intracerebral streptozotocin (i.c. STZ) model replicates the full range of abnormalities in sporadic AD. T3D-959, an orally active PPAR-delta/gamma agonist remediates neurocognitive deficits and AD neuropathology in the i.c. STZ model.

OBJECTIVE

This study characterizes the effects of T3D-959 on AD biomarkers, insulin/IGF/IRS signaling through Akt pathways, and neuroinflammation in an i.c. STZ model.

METHODS

Long Evans rats were treated with i.c. STZ or saline, followed by daily oral doses of T3D-959 (1 mg/kg) or saline initiated 1 day (T3D-959-E) or 7 days (T3D-959-L) later through Experimental Day 28. Protein and phospho-protein expression and pro-inflammatory cytokine activation were measured in temporal lobe homogenates by duplex or multiplex bead-based ELISAs.

RESULTS

i.c. STZ treatments caused neurodegeneration with increased pTau, AβPP, Aβ42, ubiquitin, and SNAP-25, and reduced levels of synaptophysin, IGF-1 receptor (R), IRS-1, Akt, p70S6K, mTOR, and S9-GSK-3β. i.c. STZ also broadly increased neuroinflammation. T3D-959 abrogated or reduced most of the AD neuropathological and biomarker abnormalities, increased/normalized IGF-1R, IRS-1, Akt, p70S6K, and S9-GSK-3β, and decreased expression of multiple pro-inflammatory cytokines. T3D-959-E or -L effectively restored insulin/IGF signaling, whereas T3D-959-L more broadly resolved neuroinflammation.

CONCLUSION

AD remediating effects of T3D-959 are potentially due to enhanced expression of key insulin/IGF signaling proteins and inhibition of GSK-3β and neuroinflammation. These effects lead to reduced neurodegeneration, cognitive impairment, and AD biomarker levels in the brain.

Simultaneous Subtotal Pancreatectomy and Streptozotocin Injection for Diabetes Modeling in Cynomolgus Monkeys

BACKGROUND

In an experimental animal model of islet transplantation, stable induction of insulin-dependent diabetes mellitus (IDDM) and islet isolation from donor pancreas are essential. Total pancreatectomy for IDDM induction and islet procurement in nonhuman primates leads to unwanted loss of exocrine function and may lead to morbidities associated with IDDM.

METHODS

IDDM induction with streptozotocin (STZ) is associated with drug toxicity of STZ and necessitates the killing of another animal for islet procurement. In this study, we performed a subtotal pancreatectomy combined with reduced STZ injection to induce IDDM and procure islets in a nonhuman primate model.

RESULTS

Twelve cynomolgus monkeys received low-dose STZ injections (60 mg/kg) simultaneously with subtotal pancreatectomy. All monkeys recovered from the procedure without complications. IDDM was induced in the animals. 57,691 ± 16,050 islets were isolated from the resected pancreas and transplanted into other monkeys.

CONCLUSIONS

Simultaneous subtotal pancreatectomy and low-dose STZ injection represent an effective and safe method to create an animal model of insulin dependence diabetes, while at the same time providing sufficient amounts of fresh islet cells for allotransplantation without requiring killing of additional animals.

Astragaloside IV prevents kidney injury caused by iatrogenic hyperinsulinemia in a streptozotocin‑induced diabetic rat model

Diabetic patients are able to manage their blood glucose with exogenous insulin but, ultimately, remain at risk of diabetic nephropathy (DN). Long‑term use of insulin may lead to iatrogenic hyperinsulinemia, which has been suggested to cause kidney injury. However, there are no effective interventions for iatrogenic hyperinsulinemia leading to kidney damage. In the present paper, the hypothesis that astragaloside IV (AS‑IV), a novel saponin purified from Astragalus membranaceus (Fisch) Bunge, may prevent DN in iatrogenic hyperinsulinemic diabetic rats through antioxidative and anti‑inflammatory mechanisms was investigated. Diabetes was induced with streptozotocin (STZ) (55 mg/kg) by intraperitoneal injection in rats. At 1 week following STZ injection, the diabetic rats were treated with Levemir subcutaneously for 4 weeks. Diabetic rat insulin levels >30 µU/ml were considered as iatrogenic hyperinsulinemia. Rats were divided into six groups (n=8 per group): Iatrogenic hyperinsulinemic rats, and iatrogenic hyperinsulinemic rats treated with Tempol and AS‑IV at 2.5, 5 and 10 mg/kg/day, intragastric infusion, for 12 weeks. The normal rats were used as a non‑diabetic control group. AS‑IV ameliorated albuminuria, mesangial cell proliferation, basement membrane thickening and podocyte foot process effacement in iatrogenic hyperinsulinemic rats. In iatrogenic hyperinsulinemic rat renal tissues, malondialdehyde, interleukin‑1β (IL‑1β), tumor necrosis factor‑α (TNF‑α), type IV collagen and laminin levels were increased, whereas glutathione peroxidase and superoxide dismutase activity levels were decreased. Nicotinamide adenine dinucleotide phosphate oxidase 4 expression and extracellular signal‑regulated kinase 1/2 (ERK1/2) activation were upregulated, and canonical transient receptor potential cation channel 6 (TRPC6) protein expression was downregulated. However, all these abnormalities were attenuated by AS‑IV. These findings suggested that AS‑IV prevented rat kidney injury caused by iatrogenic hyperinsulinemia by inhibiting oxidative stress, IL‑1β and TNF‑α overproduction, downregulating ERK1/2 activation, and upregulating TRPC6 expression.

Altered temporal lobe white matter lipid ion profiles in an experimental model of sporadic Alzheimer's disease

BACKGROUND

White matter is an early and important yet under-evaluated target of Alzheimer's disease (AD). Metabolic impairments due to insulin and insulin-like growth factor resistance contribute to white matter degeneration because corresponding signal transduction pathways maintain oligodendrocyte function and survival.

METHODS

This study utilized a model of sporadic AD in which adult Long Evans rats administered intracerebral streptozotocin (i.c. STZ) developed AD-type neurodegeneration. Temporal lobe white matter lipid ion profiles were characterized by matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS).

RESULTS

Although the lipid ion species expressed in the i.c. STZ and control groups were virtually identical, i.c. STZ mainly altered the abundances of various lipid ions. Correspondingly, the i.c. STZ group was distinguished from control by principal component analysis and data bar plots. i.c. STZ mainly reduced expression of lipid ions with low m/z's (less than 810) as well as the upper range m/z lipids (m/z 964-986), and increased expression of lipid ions with m/z's between 888 and 937. Phospholipids were mainly included among the clusters inhibited by i.c. STZ, while both sulfatides and phospholipids were increased by i.c. STZ. However, Chi-Square analysis demonstrated significant i.c. STZ-induced trend reductions in phospholipids and increases in sulfatides (P<0.00001).

CONCLUSIONS

The i.c. STZ model of sporadic AD is associated with broad and sustained abnormalities in temporal lobe white matter lipids. The findings suggest that the i.c. STZ model could be used for pre-clinical studies to assess therapeutic measures for their ability to restore white matter integrity in AD.

Deletion of FoxO1, 3, and 4 in Osteoblast Progenitors Attenuates the Loss of Cancellous Bone Mass in a Mouse Model of Type 1 Diabetes

Type 1 diabetes is associated with osteopenia and increased fragility fractures, attributed to reduced bone formation. However, the molecular mechanisms mediating these effects remain unknown. Insulin promotes osteoblast formation and inhibits the activity of the FoxO transcription factors. FoxOs, on the other hand, inhibit osteoprogenitor proliferation and bone formation. Here, we investigated whether FoxOs play a role in the low bone mass associated with type 1 diabetes, using mice lacking FoxO1, 3, and 4 in osteoprogenitor cells (FoxO1,3,4ΔOsx1-Cre ). Streptozotocin-induced diabetes caused a reduction in bone mass and strength in FoxO-intact mice. In contrast, cancellous bone was unaffected in diabetic FoxO1,3,4ΔOsx1-Cre mice. The low bone mass in the FoxO-intact diabetic mice was associated with decreased osteoblast number and bone formation, as well as decreased expression of the anti-osteoclastogenic cytokine osteoprotegerin (OPG) and increased osteoclast number. FoxO deficiency did not alter the effects of diabetes on bone formation; however, it did prevent the decrease in OPG and the increase in osteoclast number. Addition of high glucose to osteoblastic cell cultures decreased OPG mRNA, indicating that hyperglycemia in and of itself contributes to diabetic bone loss. Taken together, these results suggest that FoxOs exacerbate the loss of cancellous bone mass associated with type 1 diabetes and that inactivation of FoxOs might ameliorate the adverse effects of insulin deficiency. © 2016 American Society for Bone and Mineral Research.

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration

BACKGROUND

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking.

OBJECTIVE

This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins.

METHODS

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs.

RESULTS

CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling.

CONCLUSION

Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

Animal Model of Gestational Diabetes Mellitus with Pathophysiological Resemblance to the Human Condition Induced by Multiple Factors (Nutritional, Pharmacological, and Stress) in Rats

This study attempts to develop an experimental gestational diabetes mellitus (GDM) animal model in female Sprague-Dawley rats. Rats were fed with high fat sucrose diet, impregnated, and induced with Streptozotocin and Nicotinamide on gestational day 0 (D0). Sleeping patterns of the rats were also manipulated to induce stress, a lifestyle factor that contributes to GDM. Rats were tested for glycemic parameters (glucose, C-peptide, and insulin), lipid profiles (total cholesterol, triglycerides, HDL, and LDL), genes affecting insulin signaling (IRS-2, AKT-1, and PCK-1), glucose transporters (GLUT-2 and GLUT-4), proinflammatory cytokines (IL-6, TNF-α), and antioxidants (SOD, CAT, and GPX) on D6 and D21. GDM rats showed possible insulin resistance as evidenced by high expression of proinflammatory cytokines, PCK-1 and CRP. Furthermore, low levels of IRS-2 and AKT-1 genes and downregulation of GLUT-4 from the initial to final phases indicate possible defect of insulin signaling. GDM rats also showed an impairment of antioxidant status and a hyperlipidemic state. Additionally, GDM rats exhibited significantly higher body weight and blood glucose and lower plasma insulin level and C-peptide than control. Based on the findings outlined, the current GDM animal model closely replicates the disease state in human and can serve as a reference for future investigations.

Effect of All-Trans Retinoic Acid on the Pancreas of Streptozotocin-Induced Diabetic Rat

All-trans Retinoic acid (atRA) is instructive for the development of endocrine pancreas and is an integral component of β-cell induction protocols. We showed that atRA induces glucose-responsive endocrine transdifferentiation of pleomorphic pancreatic ductal adenocarcinoma cells in vitro. This study aimed to detect the role of atRA in improving the histological changes of the pancreas in diabetic rats. Forty young male Wistar rats were used and divided into three groups. Group I: normal vehicle control (N = 5). Group II: streptozotocin-induced diabetic rats (N = 20) were followed up at 0.0, 1, 2, and 4 weeks. Group III: streptozotocin-induced diabetic rats (N = 15) treated with atRA (2.5 mg/kg/day), were followed up at 1, 2, and 4 weeks. Specimens from the pancreas were processed for light, electron microscopy and pancreatic insulin mRNA expression. Blood samples were assayed for the levels of glucose, insulin, and total peroxides. In the atRA-treated group, the number of the islets and the islet area significantly increased. Strong insulin-immunoreactive endocrine-like cells were observed nearby the pancreatic acini and the interlobular ducts. Interestingly, insulin-positive cells seemed to arise from pancreatic acinar and ductal epithelium. Ultrastructurally, ß-cells, acinar, and ductal cells restored their normal appearance. Pancreatic insulin mRNA and blood indices were almost normalized. AtRA improved the histological changes of the pancreas and the blood indices in diabetic rats.

Tobacco Smoke-Induced Brain White Matter Myelin Dysfunction: Potential Co-Factor Role of Smoking in Neurodegeneration

BACKGROUND

Meta-analysis studies showed that smokers have increased risk for developing Alzheimer's disease (AD) compared with non-smokers, and neuroimaging studies revealed that smoking damages white matter structural integrity.

OBJECTIVE

The present study characterizes the effects of side-stream (second hand) cigarette smoke (CS) exposures on the expression of genes that regulate oligodendrocyte myelin-synthesis, maturation, and maintenance and neuroglial functions.

METHODS

Adult male A/J mice were exposed to air (8 weeks; A8), CS (4 or 8 weeks; CS4, CS8), or CS8 followed by 2 weeks recovery (CS8 + R). The frontal lobes were used for histology and qRT-PCR analysis.

RESULTS

Luxol fast blue, Hematoxylin and Eosin stained histological sections revealed CS-associated reductions in myelin staining intensity and narrowing of the corpus callosum. CS exposures broadly decreased mRNA levels of immature and mature oligodendrocyte myelin-associated, neuroglial, and oligodendrocyte-related transcription factors. These effects were more prominent in the CS8 compared with CS4 group, suggesting that molecular abnormalities linked to white matter atrophy and myelin loss worsen with duration of CS exposure. Recovery normalized or upregulated less than 25% of the suppressed genes; in most cases, inhibition of gene expression was either sustained or exacerbated.

CONCLUSION

CS exposures broadly inhibit expression of genes needed for myelin synthesis and maintenance. These adverse effects often were not reversed by short-term CS withdrawal. The results support the hypothesis that smoking contributes to white matter degeneration, and therefore could be a key risk factor for a number of neurodegenerative diseases, including AD.

Challenges and issues with streptozotocin-induced diabetes - A clinically relevant animal model to understand the diabetes pathogenesis and evaluate therapeutics

Streptozotocin (STZ) has been extensively used over the last three decades to induce diabetes in various animal species and to help screen for hypoglycemic drugs. STZ induces clinical features in animals that resemble those associated with diabetes in humans. For this reason STZ treated animals have been used to study diabetogenic mechanisms and for preclinical evaluation of novel antidiabetic therapies. However, the physiochemical characteristics and associated toxicities of STZ are still major obstacles for researchers using STZ treated animals to investigate diabetes. Another major challenges in STZ-induced diabetes are sustaining uniformity, suitability, reproducibility and induction of diabetes with minimal animal lethality. Lack of appropriate use of STZ was found to be associated with increased mortality and animal suffering. During STZ use in animals, attention should be paid to several factors such as method of preparation of STZ, stability, suitable dose, route of administration, diet regimen, animal species with respect to age, body weight, gender and the target blood glucose level used to represent hyperglycemia. Therefore, protocol for STZ-induced diabetes in experimental animals must be meticulously planned. This review highlights specific skills and strategies involved in the execution of STZ-induced diabetes model. The present review aims to provide insight into diabetogenic mechanisms of STZ, specific toxicity of STZ with its significance and factors responsible for variations in diabetogenic effects of STZ. Further this review also addresses ways to minimize STZ-induced mortality, suggests methods to improve STZ-based experimental models and best utilize them for experimental studies purported to understand diabetes pathogenesis and preclinical evaluation of drugs.

Differential Contributions of Alcohol and Nicotine-Derived Nitrosamine Ketone (NNK) to White Matter Pathology in the Adolescent Rat Brain

AIM

Epidemiologic studies have demonstrated high rates of smoking among alcoholics, and neuroimaging studies have detected white matter atrophy and degeneration in both smokers and individuals with alcohol-related brain disease (ARBD). These findings suggest that tobacco smoke exposure may be a co-factor in ARBD. The present study examines the differential and additive effects of tobacco-specific nitrosamine (NNK) and ethanol exposures on the structural and functional integrity of white matter in an experimental model.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% ethanol for 8 weeks. In weeks 3-8, rats were treated with nicotine-derived nitrosamine ketone (NNK) (2 mg/kg, 3×/week) or saline by i.p. injection. In weeks 7-8, the ethanol group was binge-administered ethanol (2 g/kg; 3×/week).

RESULTS

Ethanol, NNK and ethanol + NNK caused striking degenerative abnormalities in white matter myelin and axons, with accompanying reductions in myelin-associated glycoprotein expression. Quantitative RT-PCR targeted array and heatmap analyses demonstrated that ethanol modestly increased, whereas ethanol + NNK sharply increased expression of immature and mature oligodendroglial genes, and that NNK increased immature but inhibited mature oligodendroglial genes. In addition, NNK modulated expression of neuroglial genes in favor of growth cone collapse and synaptic disconnection. Ethanol- and NNK-associated increases in FOXO1, FOXO4 and NKX2-2 transcription factor gene expression could reflect compensatory responses to brain insulin resistance in this model.

CONCLUSION

Alcohol and tobacco exposures promote ARBD by impairing myelin synthesis, maturation and integrity via distinct but overlapping mechanisms. Public health measures to reduce ARBD should target both alcohol and tobacco abuses.

Differential Contributions of Alcohol and the Nicotine-Derived Nitrosamine Ketone (NNK) to Insulin and Insulin-Like Growth Factor Resistance in the Adolescent Rat Brain

AIMS

Since epidemiologic studies suggest that tobacco smoke toxins, e.g. the nicotine-derived nitrosamine ketone (NNK) tobacco-specific nitrosamine, can be a co-factor in alcohol-related brain disease (ARBD), we examined the independent and additive effects of alcohol and NNK exposures on spatial learning/memory, and brain insulin/IGF signaling, neuronal function and oxidative stress.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% caloric ethanol for 8 weeks. During weeks 3-8, rats were treated with i.p. NNK (2 mg/kg, 3×/week) or saline. In weeks 7-8, ethanol groups were binge-administered ethanol (2 g/kg; 3×/week). In week 8, at 12 weeks of age, rats were subjected to Morris Water Maze tests. Temporal lobes were used to assess molecular indices of insulin/IGF resistance, oxidative stress and neuronal function.

RESULTS

Ethanol and NNK impaired spatial learning, and NNK ± ethanol impaired memory. Linear trend analysis demonstrated worsening performance from control to ethanol, to NNK, and then ethanol + NNK. Ethanol ± NNK, caused brain atrophy, inhibited insulin signaling through the insulin receptor and Akt, activated GSK-3β, increased protein carbonyl and 3-nitrotyrosine, and reduced acetylcholinesterase. NNK increased NTyr. Ethanol + NNK had synergistic stimulatory effects on 8-iso-PGF-2α, inhibitory effects on p-p70S6K, tau and p-tau and trend effects on insulin-like growth factor type 1 (IGF-1) receptor expression and phosphorylation.

CONCLUSIONS

Ethanol, NNK and combined ethanol + NNK exposures that begin in adolescence impair spatial learning and memory in young adults. The ethanol and/or NNK exposures differentially impair insulin/IGF signaling through neuronal growth, survival and plasticity pathways, increase cellular injury and oxidative stress and reduce expression of critical proteins needed for neuronal function.

Kidney Versus Islet Allograft Survival After Induction of Mixed Chimerism With Combined Donor Bone Marrow Transplantation

We have previously reported successful induction of transient mixed chimerism and long-term acceptance of renal allografts in MHC mismatched nonhuman primates. In this study, we attempted to extend this tolerance induction approach to islet allografts. A total of eight recipients underwent MHC mismatched combined islet and bone marrow (BM) transplantation after induction of diabetes by streptozotocin. Three recipients were treated after a nonmyeloablative conditioning regimen that included low-dose total body and thymic irradiation, horse Atgam (ATG), six doses of anti-CD154 monoclonal antibody (mAb), and a 1-month course of cyclosporine (CyA) (Islet A). In Islet B, anti-CD8 mAb was administered in place of CyA. In Islet C, two recipients were treated with Islet B, but without ATG. The results were compared with previously reported results of eight cynomolgus monkeys that received combined kidney and BM transplantation (Kidney A) following the same conditioning regimen used in Islet A. The majority of kidney/BM recipients achieved long-term renal allograft survival after induction of transient chimerism. However, prolonged islet survival was not achieved in similarly conditioned islet/BM recipients (Islet A), despite induction of comparable levels of chimerism. In order to rule out islet allograft loss due to CyA toxicity, three recipients were treated with anti-CD8 mAb in place of CyA. Although these recipients developed significantly superior mixed chimerism and more prolonged islet allograft survival (61, 103, and 113 days), islet function was lost soon after the disappearance of chimerism. In Islet C recipients, neither prolonged chimerism nor islet survival was observed (30 and 40 days). Significant improvement of mixed chimerism induction and islet allograft survival were achieved with a CyA-free regimen that included anti-CD8 mAb. However, unlike the kidney allograft, islet allograft tolerance was not induced with transient chimerism. Induction of more durable mixed chimerism may be necessary for induction of islet allograft tolerance.

Effects of curcumin and captopril on the functions of kidney and nerve in streptozotocin-induced diabetic rats: role of angiotensin converting enzyme 1

Oxidative stress and inflammation are involved in the development and progression of diabetes and its complications. The renin-angiotensin system also plays an important role in the pathogenesis of diabetes and its complications. We hypothesized that curcumin and captopril would restore the kidney and nerve functions of diabetic rats through their angiotensin converting enzyme 1 (ACE1) inhibiting activity as well as their antioxidant and anti-inflammatory effects. Diabetes was induced by a single intraperitoneal injection of streptozotocin (100 mg·kg(-1) body weight). One week after induction of diabetes, rats were treated with 100 mg·kg(-1)·day(-1) curcumin or 50 mg·kg(-1)·day(-1) captopril orally for 6 weeks. Compared with diabetic control rats, curcumin- or captopril-treated diabetic rats had significantly improved blood glucose, lipid profile, kidney/body weight ratio, serum creatinine, blood urea nitrogen (BUN), and pain thresholds assessed by Von Frey filaments, hot plate test, and tail-flick test. Diabetic control rats showed increased levels of total peroxide, renal and neural tumor necrosis factor-α and interleukin-10, and renal ACE1 compared with nondiabetic rats. Although treatment with either curcumin or captopril restored the altered variables, captopril was more effective in reducing these variables. ACE1 was positively correlated with BUN and creatinine and negatively correlated with paw withdrawal threshold, hot plate reaction time, and tail-flick latency, suggesting a possible causal relationship. We conclude that curcumin and captopril protect against diabetic nephropathy and neuropathy by inhibiting ACE1 as well as oxidation and inflammation. These findings suggest that curcumin and captopril may have a role in the treatment of diabetic nephropathy and neuropathy.

Successful pharmaceutical-grade streptozotocin (STZ)-induced hyperglycemia in a conscious tethered baboon (Papio hamadryas) model

BACKGROUND

Non-human primate (NHP) diabetic models using chemical ablation of β-cells with STZ have been achieved by several research groups. Chemotherapeutic STZ could lead to serious adverse events including nephrotoxicity, hepatotoxicity, and mortality.

METHODS

We implemented a comprehensive therapeutic strategy that included the tether system, permanent indwelling catheter implants, an aggressive hydration protocol, management for pain with IV nubain and anxiety with IV midazolam, moment-by-moment monitoring of glucose levels post-STZ administration, and continuous intravenous insulin therapy.

RESULTS

A triphasic response in blood glucose after STZ administration was fully characterized. A dangerous hypoglycemic phase was also detected in all baboons. Other significant findings were hyperglycemia associated with low levels of plasma leptin, insulin and C-peptide concentrations, hyperglucagonemia, and elevated non-esterified fatty acids (NEFA) concentrations.

CONCLUSIONS

We successfully induced frank diabetes by IV administering a single dose of pharmaceutical-grade STZ safely and without adverse events in conscious tethered baboons.

Potential contributions of the tobacco nicotine-derived nitrosamine ketone (NNK) in the pathogenesis of steatohepatitis in a chronic plus binge rat model of alcoholic liver disease

AIMS

Alcoholic liver disease (ALD) is linked to binge drinking and cigarette smoking. Heavy chronic ± binge alcohol, or low-level exposures to dietary nitrosamines cause steatohepatitis with insulin resistance and oxidative stress in animal models. This study examines hepatotoxic effects of sub-mutagenic exposures to tobacco-specific nitrosamine (NNK) in relation to ALD.

METHODS

Long Evans rats were fed liquid diets containing 0 or 26% (caloric) ethanol (EtOH) for 8 weeks. In Weeks 3 through 8, rats were treated with NNK (2 mg/kg) or saline by i.p. injection, 3×/week, and in Weeks 7 and 8, EtOH-fed rats were binge-administered 2 g/kg EtOH 3×/week; controls were given saline.

RESULTS

EtOH ± NNK caused steatohepatitis with necrosis, disruption of the hepatic cord architecture, ballooning degeneration, early fibrosis, mitochondrial cytopathy and ER disruption. Severity of lesions was highest in the EtOH+NNK group. EtOH and NNK inhibited insulin/IGF signaling through Akt and activated pro-inflammatory cytokines, while EtOH promoted lipid peroxidation, and NNK increased apoptosis. O(6)-methyl-Guanine adducts were only detected in NNK-exposed livers.

CONCLUSION

Both alcohol and NNK exposures contribute to ALD pathogenesis, including insulin/IGF resistance and inflammation. The differential effects of EtOH and NNK on adduct formation are critical to ALD progression among alcoholics who smoke.

Role of endothelial nitric oxide synthase in diabetic nephropathy: lessons from diabetic eNOS knockout mice

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease in many countries. The animal models that recapitulate human DN undoubtedly facilitate our understanding of this disease and promote the development of new diagnostic markers and therapeutic interventions. Based on the clinical evidence showing the association of eNOS dysfunction with advanced DN, we and others have created diabetic mice that lack eNOS expression and shown that eNOS-deficient diabetic mice exhibit advanced nephropathic changes with distinct features of progressive DN, including pronounced albuminuria, nodular glomerulosclerosis, mesangiolysis, and arteriolar hyalinosis. These studies clearly defined a critical role of eNOS in DN and developed a robust animal model of this disease, which enables us to study the pathogenic mechanisms of progressive DN. Further, recent studies with this animal model have explored the novel mechanisms by which eNOS deficiency causes advanced DN and provided many new insights into the pathogenesis of DN. Therefore, here we summarize the findings obtained with this animal model and discuss the roles of eNOS in DN, unresolved issues, and future investigations of this animal model study.

The effects of transdermal insulin treatment of streptozotocin-induced diabetic rats on kidney function and renal expression of glucose transporters

The tight glycemic control required to attenuate chronic complications in type 1 diabetes mellitus requires multiple daily injections of bolus insulin which cause hyperinsulinemic edema and hypertension due to Na(+) retention. Reports indicate that pectin insulin (PI)-containing dermal patches sustain controlled insulin release into the bloodstream of streptozotocin (STZ)-induced diabetic rats. This study investigated whether PI dermal patches can improve the impaired renal function in diabetes. PI patches were prepared by dissolving pectin/insulin in deionized water and solidified with CaCl(2). Short-term (five weeks) effects of thrice daily treatments with PI patches on renal function and urinary glucose outputs were assessed in diabetic animals. Blood and kidney samples were collected after five weeks for measurements of selected biochemical parameters. Blood was also collected for insulin measurement 6 h following treatments. The low plasma insulin concentrations exhibited by STZ-induced diabetic rats were elevated by the application of insulin-containing dermal patches to levels comparable with control non-diabetic rats. Untreated STZ-induced diabetic rats exhibited elevated urinary glucose, K(+) outputs and depressed urinary Na(+) outputs throughout the 5-week period. Treatment with PI dermal patches increased urinary Na(+) output and reduced urine flow, urinary glucose and K(+) excretion rates in weeks 4 and 5. PI dermal patches increased GFR of diabetic rats with concomitant reduction of plasma creatinine concentrations. Transdermal insulin treatment also decreased the renal expressions of GLUT1 and SGLT1 of STZ-induced diabetic rats. We conclude that PI dermal patches deliver physiologically relevant amounts of insulin that can improve kidney function in diabetes.

Prevention of nonimmunologic loss of transplanted islets in monkeys

The nonimmunologic loss of islets in the pre-, peri-, and early post-islet transplant periods is profound. To determine the potential role that transplantation of only a marginal mass of functioning beta cells may play in triggering late nonimmunologic graft loss, we studied the effect of treatment with alpha-1-antitrypsin (AAT) in the autologous cynomolgus islet transplant model. A marginal mass of autologous islets, that is islets prepared from 70% to 80% of the pancreas, was transplanted at 1600-4100 IEQ/kg into subtotal pancreatectomized, streptozotocin-treated and insulin-deficient diabetic hosts. In this marginal mass islet transplant model, islet function is insidiously lost over time and diabetes recurs in all untreated monkeys by 180 days posttransplantation. Short-term treatment with AAT, an acute phase reactant, in the peri-transplant period serves to terminate inflammation through effects upon expression of TGFβ, NFκB and AKT and favorably altering expression of cell death and survival pathways, as detected by a system biology approach and histology. These effects enabled functional expansion of the islet mass in transplanted hosts such that graft function improves rather than deteriorating over time.

Relationships between diabetes and cognitive impairment

Epidemics of obesity, diabetes, nonalcoholic fatty liver disease, and cognitive impairment/Alzheimer disease have emerged over the past 3 to 4 decades. These diseases share in common target-organ insulin resistance with a constellation of molecular and biochemical abnormalities that lead to organ/tissue degeneration over time. This article discusses the fundamental links among these diseases and how peripheral organ insulin resistance diseases contribute to cognitive impairment and neurodegeneration. A future role of endocrinologists and diabetologists could be to provide integrative diagnostic and treatment approaches for this collection of diseases that seem to share pathophysiological and pathogenetic bases.

Streptozotocin-associated lymphopenia in cynomolgus monkeys

Streptozotocin (STZ) is used to induce diabetes in experimental animals. It has a variety of adverse effects, ranging from nausea, emesis, and weight loss to liver damage, renal failure, and metabolic acidosis. STZ also has effects on the immune system, being associated with lymphopenia in rodents, the mechanism of which is not fully understood. We present data on a significant STZ-associated reduction in lymphocyte count in nonhuman primates. We report a significant reduction in absolute lymphocyte count; in 2 monkeys, the lymphopenia persisted for >100 d. However, a significant increase in absolute monocyte count was noted. Furthermore, an increase in serum monocyte chemoattractant protein-1 (MCP-1) was observed. The reduction in lymphocyte numbers may contribute to immunomodulation that may be beneficial to a subsequent islet graft, and may reduce the need for immunosuppressive therapy. The increase in monocytes and MCP-1, however, may be detrimental to the islet graft. Studies are warranted to explore the mechanism by which STZ has its effect.

Nonhuman primate models of type 1 diabetes mellitus for islet transplantation

Islet transplantation is an attractive treatment of type 1 diabetes mellitus (T1DM). Animal models of diabetes mellitus (DM) contribute a lot to the experimental studies of islet transplantation and to evaluations of isolated islet grafts for future clinical applications. Diabetic nonhuman primates (NHPs) represent the suitable models of DMs to better evaluate the effectiveness of islet transplantation, to assess new strategies for controlling blood glucose (BG), relieving immune rejection, or prolonging islet survival, and eventually to translate the preclinical data into tangible clinical practice. This review introduces some NHP models of DM, clarifies why and how the models should be used, and elucidates the usefulness and limitations of the models in islet transplantation.

Brain metabolic dysfunction at the core of Alzheimer's disease

Growing evidence supports the concept that Alzheimer's disease (AD) is fundamentally a metabolic disease with molecular and biochemical features that correspond with diabetes mellitus and other peripheral insulin resistance disorders. Brain insulin/IGF resistance and its consequences can readily account for most of the structural and functional abnormalities in AD. However, disease pathogenesis is complicated by the fact that AD can occur as a separate disease process, or arise in association with systemic insulin resistance diseases, including diabetes, obesity, and non-alcoholic fatty liver disease. Whether primary or secondary in origin, brain insulin/IGF resistance initiates a cascade of neurodegeneration that is propagated by metabolic dysfunction, increased oxidative and ER stress, neuro-inflammation, impaired cell survival, and dysregulated lipid metabolism. These injurious processes compromise neuronal and glial functions, reduce neurotransmitter homeostasis, and cause toxic oligomeric pTau and (amyloid beta peptide of amyloid beta precursor protein) AβPP-Aβ fibrils and insoluble aggregates (neurofibrillary tangles and plaques) to accumulate in brain. AD progresses due to: (1) activation of a harmful positive feedback loop that progressively worsens the effects of insulin resistance; and (2) the formation of ROS- and RNS-related lipid, protein, and DNA adducts that permanently damage basic cellular and molecular functions. Epidemiologic data suggest that insulin resistance diseases, including AD, are exposure-related in etiology. Furthermore, experimental and lifestyle trend data suggest chronic low-level nitrosamine exposures are responsible. These concepts offer opportunities to discover and implement new treatments and devise preventive measures to conquer the AD and other insulin resistance disease epidemics.

Development of Canine Models of Type 1 Diabetes With Partial Pancreatectomy and the Administration of Streptozotocin

We created canine models of type 1 diabetes that were suitable for the assessment of cell therapies, such as islet transplantation and bioartificial pancreas, with low-dose streptozotocin (STZ) injection and partial pancreatectomy. In our model, a 50% pancreatectomy was performed with general anesthesia, followed by systemic injection of 35 mg/kg STZ into a vein of the foreleg. Four weeks after the administration of STZ, the fasting blood glucose level of our model dogs was found to be over 200 mg/dl twice on different days, and we could not detect any canine insulin by the intravenous glucose tolerance test (IVGTT). We therefore diagnosed the dogs to have induced diabetes. Some studies have reported high-dose STZ to be very toxic for both the kidney and liver, and therefore a lower dose is desirable to induce diabetic models without any associated kidney or liver damage. We think that the combination of a partial pancreatectomy can thus make it possible to reduce the dose of STZ, and it is therefore useful for the creation of type 1 diabetes models. We believe that our model is a safe and reliable model for type 1 diabetes in canines to assess the efficacy of pancreas-targeted cell therapies.

Management of adverse side-effects after chemotherapy in macaques as exemplified by streptozotocin: case studies and recommendations

The chemotherapeutic streptozotocin is used for induction of diabetes in animal models including non-human primates. Being a cytotoxic nitrosourea compound, it can be associated with adverse events (AEs), mainly nausea and emesis, nephrotoxicity, elevated liver transaminase levels, pulmonary oedema and, most prominently, metabolic acidosis: these can be severe in some cases. The incidence and gravity are to some extent related to the characteristics of the individual animal, diagnostic tools, prompt recognition of symptoms and supportive measures. Careful animal selection, dose adaptation and supportive actions such as renal protective hydration are the main tools in managing AEs, but do not fully eliminate unavoidable and sometimes life-threatening conditions. In our centre we have built experience in a cohort of 78 cynomolgus and rhesus macaques in which six cases manifested severe AEs (8%). This experience has prompted implementation of strategies for early detection and management of adverse effects, together with an animal refinement programme. We present here specific pretreatment regimens, post-infusion laboratory evaluations, and flow charts to assess/treat metabolic acidosis and precipitating factors. Case reports of the six animals with severe AEs are presented to illustrate management of AEs, especially metabolic acidosis, and criteria for early euthanasia where appropriate. We conclude that improved monitoring and validated tools allow for optimal management of adverse effects in an early stage of their manifestation. Reduced morbidity and mortality not only improve individual animal wellbeing but also avoid model-induced confounding that diminishes the translational value of the experimental protocol.

Prolonged survival of allogeneic islets in cynomolgus monkeys after short-term triple therapy

Preclinical studies in nonhuman primates (NHP) are particularly useful to evaluate the safety and efficacy of new therapeutic proteins developed for use in clinical transplantation. We hypothesized that a treatment that selectively destroys activated cytopathic donor reactive T cells while sparing resting and immunoregulatory T cells in a mouse model might also produce long-term drug-free engraftment and tolerance without the hazards of lymphopenia in the challenging nonhuman primate islet allograft model. Short-term treatment with a regimen consisting of rapamycin, and IL-2.Ig plus mutant antagonist-type IL-15.Ig cytolytic fusion proteins (triple therapy) posttransplantation results in prolonged, drug-free engraftment of cynomolgus islet allografts. Moreover slow progressive loss of islet function in some recipients was not associated with obvious pathologic evidence of rejection.

Characterizing the induction of diabetes in juvenile cynomolgus monkeys with different doses of streptozotocin

Juvenile (2-23 years old) cynomolgus monkeys are frequently used as recipients in non-human primate islet transplantation studies. The aim of this study was to examine the effects of different doses of streptozotocin (STZ), and find the optimal dose for inducing diabetes in these monkeys. Fifteen juvenile (2-3 years old) cynomolgus monkeys were separated into three groups and administered with different doses of STZ (100, 68 or 60 mg kg(-1)). Basal and glucose-stimulated blood glucose, insulin, and C-peptide levels, as well as body weights were monitored. Hepatic and renal function tests and pancreatic immunohistochemistry were performed before and after STZ treatment. Monkeys treated with both 100 and 68 mg kg(-1) of STZ exhibited continuous hyperglycemia, which coincided with a nearly complete loss of islet β-cells. Two monkeys received 60 mg kg(-1) of STZ, but only one became completely diabetic. During the first week following STZ treatment, hepatic and renal function slightly increased in these three groups. However, 24 hours post-STZ, serum total bile acid levels were significantly increased in monkeys treated with 100 mg kg(-1) than those treated with 68 mg kg(-1) of STZ (P<0.05). These data suggest that 100 mg kg(-1) and 68 mg kg(-1) of STZ can safely induce diabetes in cynomolgus monkeys aged 2-3 years, but 68 mg kg(-1) of STZ, rather than 100 mg kg(-1) of STZ, may be more appropriate for inducing diabetes in these monkeys. Furthermore, body surface area, rather than body weight, was a more reliable determinant of dosage, where 700 mg m(-2) of STZ should be the lower limit for inducing diabetes in juvenile monkeys.

Therapeutic targets of brain insulin resistance in sporadic Alzheimer's disease

Growing evidence supports roles for brain insulin and insulin-like growth factor (IGF) resistance and metabolic dysfunction in the pathogenesis of Alzheimer's disease (AD). Whether the underlying problem stems from a primary disorder of central nervous system (CNS) neurons and glia, or secondary effects of systemic diseases such as obesity, Type 2 diabetes, or metabolic syndrome, the end-results include impaired glucose utilization, mitochondrial dysfunction, increased oxidative stress, neuroinflammation, and the propagation of cascades that result in the accumulation of neurotoxic misfolded, aggregated, and ubiquitinated fibrillar proteins. This article reviews the roles of impaired insulin and IGF signaling to AD-associated neuronal loss, synaptic disconnection, tau hyperphosphorylation, amyloid-beta accumulation, and impaired energy metabolism, and discusses therapeutic strategies and lifestyle approaches that could be used to prevent, delay the onset, or reduce the severity of AD. Finally, it is critical to recognize that AD is heterogeneous and has a clinical course that fully develops over a period of several decades. Therefore, early and multi-modal preventive and treatment approaches should be regarded as essential.

Refining the high-dose streptozotocin-induced diabetic non-human primate model: an evaluation of risk factors and outcomes

In preparation for islet transplantation, diabetes was induced using streptozotocin (STZ) in non-human primates ranging from juveniles to adults with diverse body types: we studied the process with respect to the diabetic state and emergence of adverse events (AEs) and their severity, and identified risk factors for clinical and laboratory AEs. Pharmaceutical-grade STZ was given based on body surface area (BSA) (1050–1250 mg/m2, equivalent to 80–108 mg/kg) or on body weight (BW) (100 mg/kg) to 54 cynomolgus and 24 rhesus macaques. AEs were related to risk factors, i.e. obesity parameters, BW and BSA, age and STZ dose in mg/m2. Clinical AEs during the first days after infusion prompted euthanasia of three animals. Except for those three animals, diabetes was successfully induced as shown by circulating C-peptide levels, the intravenous glucose tolerance test and/or arginine stimulation test. C-peptide after infusion weakly correlated ( P = 0.048) with STZ dose in mg/m2. Grade ≥3 nephrotoxicity or hepatotoxicity (serum markers >3× baseline or >5 × baseline, respectively) occurred in about 10% of cases and were generally mild and reversible. Grade ≥2 clinical AEs occurred in seven of 78 animals, reversed in four cases and significantly correlated with obesity parameters. Taking girth-to-height ratio (GHtR) as an indicator of obesity, with threshold value 0.92–0.95, the positive predictive value of obesity for AEs was 92% and the specificity 94%. We conclude that diabetes is successfully induced in non-obese animals using a 100 mg/kg pharmaceutical grade STZ dose. Obesity is a significant risk factor, and animals with a higher than normal GHtR should preferably receive a lower dose. The incidence of relevant clinical or laboratory AEs is low. Careful monitoring and supportive medical intervention can result in recovery of AEs.

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.

Beta-5 score to evaluate pig islet graft function in a primate pre-clinical model

BACKGROUND

We developed a composite scoring system to accurately assess pig islet function in pre-clinical primate studies.

METHODS

Two scoring methods that have been clinically validated in human islet allotransplantation were tested in six non-diabetic and nine streptozotocin (STZ)-induced diabetic primates: (i) SUITO index=[1500 × fasting C-peptide (ng/ml)]/[fasting blood glucose (FBG, mg/dl) - 63] and (ii) CP/G ratio =[fasting C-peptide (ng/ml) × 100]/FBG (mg/dl). Both scores were analysed as a function of the β-cell mass of the native primate pancreas. Next, a proposed β5 score based on FBG values, daily glycosuria, post-prandial glycosuria, polydipsia, and polyuria was validated on the same primates. Ranges of normal and pathologic values for each parameter were assessed during 5 months in non-diabetic and diabetic primates, respectively. Finally, scores were tested on the nine STZ-induced diabetic primates, four of which were transplanted with microencapsulated pig islets and five with macroencapsulated pig islets. All parameters required for each score were measured prior to transplantation and up to 12 weeks post-transplantation. For the CP/G ratio after transplantation, primate C-peptide was replaced by porcine C-peptide.

RESULTS

The Suito index was not correlated with the pancreatic β-cell mass in contrast to the CP/G ratio (R(2) = 0.17, P = 0.645 vs. R(2) = 0.76, P = 0.003; respectively). The internal consistency of the parameters implied by the β5 score was confirmed by a Cronbach's alpha test of 0.97. Diabetes was confirmed by a significant decrease in the CP/G ratio and the β5 score before and after diabetes induction, respectively. After transplantation, a significant correlation was found between the CP/G ratio and the β5 score, which reflected the functionality of pig islet xenografts and diabetes control. In addition, the CP/G ratio and β5 score were correlated with the glycosylated hemoglobin course after transplantation and diabetes correction with macroencapsulated pig islets.

CONCLUSION

The proposed β5 score provides a valid tool to accurately assess islet transplantation in a primate pre-clinical model.

Characterization and validation of a streptozotocin-induced diabetes model in the vervet monkey

INTRODUCTION

Streptozotocin (STZ), preferentially toxic to pancreatic beta cells, is commonly used to model Type 1 diabetes mellitus (DM) in numerous species, including nonhuman primates.

METHODS

We induced DM in twenty vervet monkeys (Chlorocebus aethiops) by intravenous administration of either 45 (n=8, STZ-45) or 55 mg/kg STZ (n=12, STZ-55); ten control (CTL) monkeys received saline.

RESULTS

Overall there was 15% mortality, likely secondary to renal toxicity. Twice-daily insulin therapy was initiated to maintain comparable glycemic control, confirmed by comparable glycated hemoglobin levels. Exogenous insulin requirements increased rapidly for 4weeks; STZ-45 insulin doses stabilized thereafter while STZ-55 doses continued to increase through 16weeks. Glucose tolerance testing and arginine-stimulated insulin secretion confirmed 80-90% reduction in pancreatic beta cell function in both groups. Body weight was reduced in all STZ monkeys, with return to baseline only in STZ-45 at 16 wks. Elevated blood urea nitrogen (BUN) and creatinine were noted in the STZ-55 group. Alkaline phosphatase (ALKP) was also increased with STZ-55 (p < 0.05 vs. CTL) whereas STZ-45 ALKP elevation resolved by study end. Red cell parameters were reduced in all STZ monkeys, but more severely in the STZ-55 group.

DISCUSSION

We have demonstrated that a model of DM can be induced and maintained in vervets with a single dose of STZ. The lower dose of STZ (45 mg/kg) significantly improved the toxicity profile without altering efficacy in inducing DM. Finally, sufficient time following induction is recommended to allow transient renal, hepatic and hematologic parameters to resolve.

Comparison of single high-dose streptozotocin with partial pancreatectomy combined with low-dose streptozotocin for diabetes induction in rhesus monkeys

Monkeys with insulin-dependent diabetes are important experimental models for islet xenotransplantation. However, with regard to diabetes induction, total pancreatectomy is a difficult operation with a high complication rate, while streptozotocin (STZ) administration may cause serious toxic effects and individual difference in metabolism. We compared two strategies involving pancreatectomy and STZ to successfully and safely induce diabetes in rhesus monkeys. Thirteen rhesus monkeys were divided into two groups: single high-dose STZ administration (80, 100 and 120 mg/kg, n = 3 for each dose) (group 1) and partial pancreatectomy (70–75%) combined with low-dose STZ (15 mg/kg, n = 4) (group 2). Induction of diabetes was evaluated by blood glucose, insulin, C-peptide, intravenous glucose tolerance test (IVGTT) and arginine stimulation test (AST). Detection of hematological and serum biochemical parameters and biopsies of pancreas, liver and kidney were periodically performed. In our study, animals in both groups developed diabetes. Serum C-peptide levels in groups 1 and 2 decreased to 0.08 ± 0.07 and 0.35 ± 0.06 nmol/L, respectively. IVGTT and AST indicated severely impaired glucose tolerance. Immunohistochemistry demonstrated that rare insulin-positive cells remained in the pancreas. In terms of STZ toxicity, four monkeys died 8–14 days after STZ administration (3 with 120 mg/kg STZ and 1 with 100 mg/kg STZ). Group 1 animals developed liver and kidney injury evidenced by increased alanine aminotransferase, aspartate aminotransferase, total cholesterol, LDL, triglyceride and blood urea nitrogen for one month, and histological abnormality including hepatic steatosis, renal glomerulus and tubular injury. Nevertheless, moderate histological injuries were seen in animals with 80 mg/kg STZ, with subsequent recovery. In contrast, group 2 animals displayed normal biochemical parameters and histology, with generally less risk of postoperative complications. We conclude that injection of 80 mg/kg STZ could induce diabetes with moderate injuries. Partial pancreatectomy with low-dose STZ is a safer and more reproducible method for inducing diabetes in rhesus monkeys.

Epidemilogical trends strongly suggest exposures as etiologic agents in the pathogenesis of sporadic Alzheimer's disease, diabetes mellitus, and non-alcoholic steatohepatitis

Nitrosamines mediate their mutagenic effects by causing DNA damage, oxidative stress, lipid peroxidation, and pro-inflammatory cytokine activation, which lead to increased cellular degeneration and death. However, the very same pathophysiological processes comprise the "unbuilding" blocks of aging and insulin-resistance diseases including, neurodegeneration, diabetes mellitus (DM), and non-alcoholic steatohepatitis (NASH). Previous studies demonstrated that experimental exposure to streptozotocin, a nitrosamine-related compound, causes NASH, and diabetes mellitus Types 1, 2 and 3 (Alzheimer (AD)-type neurodegeneration). Herein, we review evidence that the upwardly spiraling trends in mortality rates due to DM, AD, and Parkinson's disease typify exposure rather than genetic-based disease models, and parallel the progressive increases in human exposure to nitrates, nitrites, and nitrosamines via processed/preserved foods. We propose that such chronic exposures have critical roles in the pathogenesis of our insulin resistance disease pandemic. Potential solutions include: 1) eliminating the use of nitrites in food; 2) reducing nitrate levels in fertilizer and water used to irrigate crops; and 3) employing safe and effective measures to detoxify food and water prior to human consumption. Future research efforts should focus on refining our ability to detect and monitor human exposures to nitrosamines and assess early evidence of nitrosamine-mediated tissue injury and insulin resistance.

Animal models of catheter-induced intimal hyperplasia in type 1 and type 2 diabetes and the effects of pharmacologic intervention

Diabetes is a complex disorder characterized by impaired insulin formation, release or action (insulin resistance), elevated blood glucose, and multiple long-term complications. It is a common endocrine disorder of humans and is associated with abnormalities of carbohydrate and lipid metabolism. There are two forms of diabetes, classified as type 1 and type 2. In type 1 diabetes, hyperglycemia is due to an absolute lack of insulin, whereas in type 2 diabetes, hyperglycemia is due to a relative lack of insulin and insulin resistance. More than 90% of people with diabetes have type 2 with varied degrees of insulin resistance. Insulin resistance is often associated with impaired insulin secretion, and hyperglycemia is a common feature in both types of diabetes, but failure to make a distinction between the types of diabetes in different animal models has led to confusion in the literature. This is particularly true in relation to cardiovascular disease in the presence of diabetes and especially the response to vascular injury, in which there are major differences between the two types of diabetes. Animal models do not completely mimic the clinical disease seen in humans. Animal models are at best analogies of the pathologic process they are designed to represent. The focus of this review is an analysis of intimal hyperplasia following catheter-induced vascular injury, including factors that may complicate comparisons between different animal models or between in vitro and in vivo studies. We examine the variables, pitfalls, and caveats that follow from the manner of induction of the injury and the diabetic state of the animal. The efficacy of selected antidiabetic drugs in inhibiting the development of the hyperplastic response is also discussed.

Streptozotocin, type I diabetes severity and bone

As many as 50% of adults with type I (T1) diabetes exhibit bone loss and are at increased risk for fractures. Therapeutic development to prevent bone loss and/or restore lost bone in T1 diabetic patients requires knowledge of the molecular mechanisms accounting for the bone pathology. Because cell culture models alone cannot fully address the systemic/metabolic complexity of T1 diabetes, animal models are critical. A variety of models exist including spontaneous and pharmacologically induced T1 diabetic rodents. In this paper, we discuss the streptozotocin (STZ)-induced T1 diabetic mouse model and examine dose-dependent effects on disease severity and bone. Five daily injections of either 40 or 60 mg/kg STZ induce bone pathologies similar to spontaneously diabetic mouse and rat models and to human T1 diabetic bone pathology. Specifically, bone volume, mineral apposition rate, and osteocalcin serum and tibia messenger RNA levels are decreased. In contrast, bone marrow adiposity and aP2 expression are increased with either dose. However, high-dose STZ caused a more rapid elevation of blood glucose levels and a greater magnitude of change in body mass, fat pad mass, and bone gene expression (osteocalcin, aP2). An increase in cathepsin K and in the ratio of RANKL/OPG was noted in high-dose STZ mice, suggesting the possibility that severe diabetes could increase osteoclast activity, something not seen with lower doses. This may contribute to some of the disparity between existing studies regarding the role of osteoclasts in diabetic bone pathology. Examination of kidney and liver toxicity indicate that the high STZ dose causes some liver inflammation. In summary, the multiple low-dose STZ mouse model exhibits a similar bone phenotype to spontaneous models, has low toxicity, and serves as a useful tool for examining mechanisms of T1 diabetic bone loss.