Effects of ketamine sedation on glucose clearance, insulin secretion and counterregulatory hormone production in baboons (Papio hamadryas)

Effects of ketamine on metabolic parameters in depressive disorders: A systematic review

BACKGROUND

Persons with Major Depressive Disorder (MDD), notably treatment-resistant depression (TRD), are differentially affected by type 2 diabetes mellitus and associated morbidity. Ketamine is highly efficacious in the treatment of adults living with MDD, notably TRD. Herein, we sought to determine the effect of ketamine on metabolic parameters in animal stress paradigms and human studies.

METHODS

We performed a comprehensive search on PubMed, OVID, and Scopus databases for primary research articles from inception to May 5, 2024. Study screening and data extraction were performed by two reviewers (S.W. and G.H.L.). Both preclinical and clinical studies were included in this review.

RESULTS

Results from the preclinical studies indicate that in experimental diabetic conditions, ketamine does not disrupt glucose-insulin homeostasis. Within adults with MDD, ketamine is associated with GLUT3 transporter upregulation and differentially affects metabolomic signatures. In adults with TRD, ketamine induces increased brain glucose uptake in the prefrontal cortex. Available evidence suggests that ketamine does not adversely affect metabolic parameters.

LIMITATIONS

There are a paucity of clinical studies evaluating the effects of ketamine on glucose-insulin homeostasis in adults with MDD.

CONCLUSIONS

Our results indicate that ketamine is not associated with significant and/or persistent disruptions in metabolic parameters. Available evidence indicates that ketamine does not adversely affect glucose-insulin homeostasis. These results underscore ketamine's efficacy and safety as an antidepressant treatment that is not associated with metabolic disturbances commonly reported with current augmentation therapies.

Quality of hematology and clinical chemistry results in laboratory and zoo nonhuman primates: Effects of the preanalytical phase. A review

Most errors in clinical pathology originate in the preanalytical phase, which includes all steps from the preparation of animals and equipment to the collection of the specimen and its management until analyzed. Blood is the most common specimen collected in nonhuman primates. Other specimens collected include urine, saliva, feces, and hair. The primary concern is the variability of blood hematology and biochemistry results due to sampling conditions with the effects of capture, restraint, and/or anesthesia. Housing and diet have fewer effects, with the exception of food restriction to reduce obesity. There has been less investigation regarding the impact of sampling conditions of nonblood specimens.

Evaluating individual biomarkers for predicting health risks in zoo-housed chimpanzees (Pan troglodytes) and bonobos (Pan paniscus)

Although biomarkers are often used for predicting morbidity and mortality in humans, similar data are lacking in our closest relatives. This study analyzed 16 biomarkers in zoo-housed chimpanzees and bonobos from serum samples collected during both routine and nonroutine veterinary immobilizations. Generalized linear and generalized linear mixed models were used to determine the efficacy of each biomarker to predict all-cause morbidity, defined as the presence of at least one chronic condition, or cardiac disease as a subset of all-cause morbidity. Cox proportional hazards models were used to examine associations between biomarkers and mortality risk from any cause. Analyses were conducted using two data sets for each species, one with all values retained (chimpanzees: n = 148; bonobos: n = 33) and the other from samples collected during routine immobilizations only (chimpanzees: n = 95; bonobos: n = 23). Consistent results across both data sets in chimpanzees included associations of higher cortisol with all-cause morbidity risk, lower creatinine with cardiac disease risk, and higher creatinine with mortality risk, and in bonobos were increased cardiac disease risk with higher cortisol and lower dehydroepiandrosterone-sulfate, fructosamine, and triglycerides. However, there were some inconsistencies between data sets, such as tumor necrosis factor-α predicting mortality risk positively in chimpanzees when all values were retained, but negatively for routine values only. Despite the close evolutionary relationships between chimpanzees and bonobos, the only result observed in both species was a negative association between albumin and mortality risk in the all values retained data sets. Thus, data suggest some biomarkers may be useful predictors of future health outcomes, although a better understanding of both individual and species variation in biomarkers and their contribution to health risks is needed.

Microencapsulated adult porcine islets transplanted intraperitoneally in streptozotocin-diabetic non-human primates

BACKGROUND

Xenogeneic donors would provide an unlimited source of islets for the treatment of type 1 diabetes (T1D). The goal of this study was to assess the function of microencapsulated adult porcine islets (APIs) transplanted ip in streptozotocin (STZ)-diabetic non-human primates (NHPs) given targeted immunosuppression.

METHODS

APIs were encapsulated in: (a) single barium-gelled alginate capsules or (b) double alginate capsules with an inner, islet-containing compartment and a durable, biocompatible outer alginate layer. Immunosuppressed, streptozotocin-diabetic NHPs were transplanted ip with encapsulated APIs, and graft function was monitored by measuring blood glucose, %HbA1c, and porcine C-peptide. At graft failure, explanted capsules were assessed for biocompatibility and durability plus islet viability and functionality. Host immune responses were evaluated by phenotyping peritoneal cell populations, quantitation of peritoneal cytokines and chemokines, and measurement of anti-porcine IgG and IgM plus anti-Gal IgG.

RESULTS

NHP recipients had reduced hyperglycemia, decreased exogenous insulin requirements, and lower percent hemoglobin A1c (%HbA1c) levels. Porcine C-peptide was detected in plasma of all recipients, but these levels diminished with time. However, relatively high levels of porcine C-peptide were detected locally in the peritoneal graft site of some recipients at sacrifice. IV glucose tolerance tests demonstrated metabolic function, but the grafts eventually failed in all diabetic NHPs regardless of the type of encapsulation or the host immunosuppression regimen. Explanted microcapsules were intact, "clean," and free-floating without evidence of fibrosis at graft failure, and some reversed diabetes when re-implanted ip in diabetic immunoincompetent mice. Histology of explanted capsules showed scant evidence of a host cellular response, and viable islets could be found. Flow cytometric analyses of peritoneal cells and peripheral blood showed similarly minimal evidence of a host immune response. Preformed anti-porcine IgG and IgM antibodies were present in recipient plasma, but these levels did not rise post-transplant. Peritoneal graft site cytokine or chemokine levels were equivalent to normal controls, with the exception of minimal elevation observed for IL-6 or IL-1β, GRO-α, I-309, IP-10, and MCP-1. However, we found central necrosis in many of the encapsulated islets after graft failure, and explanted islets expressed endogenous markers of hypoxia (HIF-1α, osteopontin, and GLUT-1), suggesting a role for non-immunologic factors, likely hypoxia, in graft failure.

CONCLUSIONS

With donor xenoislet microencapsulation and host immunosuppression, APIs corrected hyperglycemia after ip transplantation in STZ-diabetic NHPs in the short term. The islet xenografts lost efficacy gradually, but at graft failure, some viable islets remained, substantial porcine C-peptide was detected in the peritoneal graft site, and there was very little evidence of a host immune response. We postulate that chronic effects of non-immunologic factors, such as in vivo hypoxic and hyperglycemic conditions, damaged the encapsulated islet xenografts. To achieve long-term function, new approaches must be developed to prevent this damage, for example, by increasing the oxygen supply to microencapsulated islets in the ip space.

Changes in Cerebral Blood Flow during an Alteration in Glycemic State in a Large Non-human Primate (Papio hamadryas sp.)

Changes in cerebral blood flow (CBF) during a hyperglycemic challenge were mapped, using perfusion-weighted MRI, in a group of non-human primates. Seven female baboons were fasted for 16 h prior to 1-h imaging experiment, performed under general anesthesia, that consisted of a 20-min baseline, followed by a bolus infusion of glucose (500 mg/kg). CBF maps were collected every 7 s and blood glucose and insulin levels were sampled at regular intervals. Blood glucose levels rose from 51.3 ± 10.9 to 203.9 ± 38.9 mg/dL and declined to 133.4 ± 22.0 mg/dL, at the end of the experiment. Regional CBF changes consisted of four clusters: cerebral cortex, thalamus, hypothalamus, and mesencephalon. Increases in the hypothalamic blood flow occurred concurrently with the regulatory response to systemic glucose change, whereas CBF declined for other clusters. The return to baseline of hypothalamic blood flow was observed while CBF was still increasing in other brain regions. The spatial pattern of extra-hypothalamic CBF changes was correlated with the patterns of several cerebral networks including the default mode network. These findings suggest that hypothalamic blood flow response to systemic glucose levels can potentially be explained by regulatory activity. The response of extra-hypothalamic clusters followed a different time course and its spatial pattern resembled that of the default-mode network.

Acute Hyperglycemia Induced by Ketamine/Xylazine Anesthesia in Rats: Mechanisms and Implications for Preclinical Models

The effects of anesthetic agents, commonly used in animal models, on blood glucose levels in fed and fasted rats were investigated. In fed Sprague-Dawley rats, ketamine (100 mg/kg)/xylazine (10 mg/kg) (KX) produced acute hyperglycemia (blood glucose 178.4 ± 8.0 mg/dl) within 20 min. The baseline blood glucose levels (104.8 ± 5.7 mg/dl) reached maximum levels (291.7 ± 23.8 mg/dl) at 120 min. Ketamine alone did not elevate glucose levels in fed rats. Isoflurane also produced acute hyperglycemia similar to KX. Administration of pentobarbital sodium did not produce hyperglycemia in fed rats. In contrast, none of these anesthetic agents produced hyperglycemia in fasted rats. The acute hyperglycemic effect of KX in fed rats was associated with decreased plasma levels of insulin, adrenocorticotropic hormone (ACTH), and corticosterone and increased levels of glucagon and growth hormone (GH). The acute hyperglycemic response to KX was dose-dependently inhibited by the specific Α2-adrenergic receptor antagonist yohimbine (1–4 mg/kg). KX-induced changes of glucoregulatory hormone levels such as insulin, GH, ACTH, and corticosterone were significantly altered by yohimbine, whereas the glucagon levels remained unaffected. In conclusion, the present study indicates that both KX and isoflurane produce acute hyperglycemia in fed rats. The effect of KX is mediated by modulation of the glucoregulatory hormones through stimulation of Α2-adrenergic receptors. Pentobarbital sodium did not produce hyperglycemia in either fed or fasted rats. Based on these findings, it is suggested that caution needs to be taken when selecting anesthetic agents, and fed or fasted state of animals in studies of diabetic disease or other models where glucose and/or glucoregulatory hormone levels may influence outcome and thus interpretation. However, fed animals are of value when exploring the hyperglycemic response to anesthetic agents.

The effect of propofol on intravenous glucose tolerance test in rhesus monkey

BACKGROUND

Many anesthetics have been shown to impair glucose metabolism and cause hyperglycemia. The aim of this study was to evaluate the effects of propofol on glucose metabolism and insulin secretion during intravenous glucose tolerance test (IVGTT) in rhesus monkey.

METHODS

Serum cortisol, blood glucose, insulin, and C-peptide concentrations during IVGTT were measured in four rhesus monkeys under either conscious state or propofol anesthesia.

RESULTS AND CONCLUSIONS

The levels of serum cortisol significantly increased under conscious condition, whereas these levels remained constant under propofol anesthesia. In propofol group, the levels of serum insulin and C-peptide significantly increased compared with those in conscious group. Accordingly, glucose disposal capacity was significantly improved, and the time to return to basal glucose levels was shortened in propofol group. This study showed that propofol significantly increased insulin and C-peptide, and the corresponding improvement in glucose disposal may be related to reduction of serum cortisol in monkey.

The effects of handling and anesthetic agents on the stress response and carbohydrate metabolism in northern elephant seals

Free-ranging animals often cope with fluctuating environmental conditions such as weather, food availability, predation risk, the requirements of breeding, and the influence of anthropogenic factors. Consequently, researchers are increasingly measuring stress markers, especially glucocorticoids, to understand stress, disturbance, and population health. Studying free-ranging animals, however, comes with numerous difficulties posed by environmental conditions and the particular characteristics of study species. Performing measurements under either physical restraint or chemical sedation may affect the physiological variable under investigation and lead to values that may not reflect the standard functional state of the animal. This study measured the stress response resulting from different handling conditions in northern elephant seals and any ensuing influences on carbohydrate metabolism. Endogenous glucose production (EGP) was measured using [6-(3)H]glucose and plasma cortisol concentration was measured from blood samples drawn during three-hour measurement intervals. These measurements were conducted in weanlings and yearlings with and without the use of chemical sedatives--under chemical sedation, physical restraint, or unrestrained. We compared these findings with measurements in adult seals sedated in the field. The method of handling had a significant influence on the stress response and carbohydrate metabolism. Physically restrained weanlings and yearlings transported to the lab had increased concentrations of circulating cortisol (F(11, 46) = 25.2, p<0.01) and epinephrine (F(3, 12) = 5.8, p = 0.01). Physical restraint led to increased EGP (t = 3.1, p = 0.04) and elevated plasma glucose levels (t = 8.2, p<0.01). Animals chemically sedated in the field typically did not exhibit a cortisol stress response. The combination of anesthetic agents (Telazol, ketamine, and diazepam) used in this study appeared to alleviate a cortisol stress response due to handling in the field without altering carbohydrate metabolism. Measures of hormone concentrations and metabolism made under these conditions are more likely to reflect basal values.

Eight week exposure to a high sugar high fat diet results in adiposity gain and alterations in metabolic biomarkers in baboons (Papio hamadryas sp.)

Background

Baboons (Papio hamadryas Sp.) develop features of the cardiometabolic syndrome and represent a clinically-relevant animal model in which to study the aetiology of the disorder. To further evaluate the baboon as a model for the study of the cardiometabolic syndrome, we developed a high sugar high fat diet and hypothesized that it could be used to induce adiposity gain and affect associated circulating biomarkers.

Methods

We developed a diet enriched with monosaccharides and saturated fatty acids that was composed of solid and liquid energy sources. We provided a group of baboons (n = 9) ad libitum access to this diet for 8 weeks. Concurrently, a control group (n = 6) was maintained with ad libitum access to a low sugar low fat baseline diet and normal water for 8 weeks. Body composition was determined by dual-energy X-ray absorptiometry and circulating metabolic biomarkers were measured using standard methodology before and after the 8 week study period.

Results

Neither body composition nor circulating biomarkers changed in the control group. Following the 8 weeks, the intervention group had a significant increase in fat mass (1.71 ± 0.98 vs. 3.23 ± 1.70 kg, p = 0.004), triglyceride (55 ± 13 vs. 109 ± 67 mg/dL, p = 0.006,), and leptin (1.19 ± 1.40 vs. 3.29 ± 2.32 ng/mL, p = 0.001) and a decline in adiponectin concentrations (33530 ± 9744 vs. 23330 ± 7863 ng/mL, p = 0.002). Percentage haemoglobin A_1C (4.0 ± 0.3 vs. 6.0 ± 1.4, p = 0.002) also increased in the intervention group.

Conclusions

Our findings indicate that when exposed to a high sugar high fat diet, young adult male baboons develop increased body fat and triglyceride concentrations, altered adipokine concentrations, and evidence of altered glucose metabolism. Our findings are in keeping with observations in humans and further demonstrate the potential utility of this highly clinically-relevant animal model for studying diet-induced metabolic dysregulation.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Cortisol responses to immobilization with Telazol or ketamine in baboons (Papio cynocephalus/anubis) and rhesus macaques (Macaca mulatta)

Little is known about the influence of Telazol on cortisol or of anesthetic agents on immunological measures, and reports of ketamine's effect on cortisol are inconsistent. We measured effects of Telazol, ketamine and blood sampling on cortisol in male rhesus macaques and male savannah baboons. We also obtained leukocyte counts in the macaques. In macaques, Telazol reduced cortisol in the morning but not in the afternoon; ketamine had no effect on cortisol in these animals. In baboons, cortisol changed little post-Telazol but increased post-ketamine. In macaques, lymphocyte numbers decreased following afternoon injection of Telazol, ketamine or saline. The injection and blood sampling process increased cortisol levels in monkeys not trained to extend an arm but exerted no effect on cortisol in trained macaques. Thus, the animals' physiological responses to blood sampling and immobilization are influenced by such variables as anesthetic agent, species, time of day, and familiarity with the blood sampling process.

Physiological effect of circulating glucagon on the hepatic membrane potential

The pancreatic hormone glucagon hyperpolarizes the liver cell membrane under various conditions. Here we investigated the physiological relevance of this effect by testing the influence of infusions of glucagon antiserum on the liver cell membrane potential in vivo. Intracellular microelectrode recordings of liver cells (up to 60/rat over 2 h) were done in anesthetized male rats. Livers were fixed in place, and recordings were done 10-30 min after intraperitoneal injections of glucagon or hepatic portal vein infusions of glucagon or specific polyclonal glucagon antibodies raised in rabbits. The isotonic lactose vehicle was used as a control for glucagon, and equal amounts of nonimmunized rabbit IgG were used as a control for glucagon antibodies. Intraperitoneal glucagon (400 microg/kg) hyperpolarized the liver cell membrane up to 12 mV, and intraportal glucagon (10 or 60 microg/kg) dose dependently hyperpolarized the liver cell membrane by 3-7 mV. Intraportal infusion of glucagon antiserum (in vitro binding capacity of 4 ng glucagon/rat) significantly depolarized the liver cell membrane by approximately 2.5 mV. The effects of both glucagon and glucagon antiserum reversed after 60-90 min. We conclude that glucagon is a physiologically important modulator of the liver cell membrane potential.

Long-term survival and function of intrahepatic islet allografts in rhesus monkeys treated with humanized anti-CD154

Reported effects of anti-CD154 treatment on autoimmunity, alloreactivity, and inflammatory events mediated by macrophages and endothelial cells indicated that it might be an ideal agent for the prevention of intrahepatic islet allograft failure. This hypothesis was tested in MHC-mismatched rhesus monkeys. Transplantation of an adequate number of viable islets resulted in engraftment and insulin independence in six of six recipients treated with anti-CD154 (hu5c8) induction plus monthly maintenance therapy (post-operative day >125, >246, >266, >405, >419, >476). Anti-CD154 (hu5c8) displayed no inhibitory effect on islet cell function. For monkeys followed for >100 days, continued improvement in graft function, as determined by first phase insulin release in response to intravenous glucose, was observed after the first 100 days post-transplant. No evidence of toxicity or infectious complications has been observed. All recipients treated with anti-CD154 became specifically nonresponsive to donor cells in mixed lymphocyte reactions. Furthermore, three monkeys are now off therapy (>113, >67, and >54 days off anti-CD154), with continued insulin independence and donor-specific mixed lymphocyte reaction hyporeactivity. In striking contrast to all previously tested strategies, transplantation of an adequate number of functional islets under the cover of anti-CD154 (hu5c8) monotherapy consistently allows for allogeneic islet engraftment and long-term insulin independence in this highly relevant preclinical model.