Decreased opioid-induced antinociception but unaltered G-protein activation in the genetic-diabetic NOD mouse

Postoperative opioid prescribing patients with diabetes: Opportunities for personalized pain management

BACKGROUND

Opioids are commonly prescribed for postoperative pain, but may lead to prolonged use and addiction. Diabetes impairs nerve function, complicates pain management, and makes opioid prescribing particularly challenging.

METHODS

This retrospective observational study included a cohort of postoperative patients from a multisite academic health system to assess the relationship between diabetes, pain, and prolonged opioid use (POU), 2008-2019. POU was defined as a new opioid prescription 3-6 months after discharge. The odds that a patient had POU was assessed using multivariate logistic regression controlling for patient factors (e.g., demographic and clinical factors, as well as prior pain and opiate use).

FINDINGS

A total of 43,654 patients were included, 12.4% with diabetes. Patients with diabetes had higher preoperative pain scores (2.1 vs 1.9, p<0.001) and lower opioid naïve rates (58.7% vs 68.6%, p<0.001). Following surgery, patients with diabetes had higher rates of POU (17.7% vs 12.7%, p<0.001) despite receiving similar opioid prescriptions at discharge. Patients with Type I diabetes were more likely to have POU compared to other patients (Odds Ratio [OR]: 2.22; 95% Confidence Interval [CI]:1.69-2.90 and OR:1.44, CI: 1.33-1.56, respectively).

INTERPRETATION

In conclusion, surgical patients with diabetes are at increased risk for POU even after controlling for likely covariates, yet they receive similar postoperative opiate therapy. The results suggest a more tailored approach to diabetic postoperative pain management is warranted.

Investigation of Opioid Growth Factor Pathway Inhibition on the Histologic Structure of Testicular Tissue and Microscopic Indices of Spermatogenesis in Adult Diabetic Mice

Background and aims: Endogenous opioids function as negative factors affecting the growth has been established. The most influential factor in the growth and differentiation of the proliferating cells is the opioid growth factor (OGF). Recently, some studies have been completed about the effects of opioid growth factor in the pathogenesis of diabetes and the beneficial effects of inhibition of this growth pathway have been demonstrated. The aim of this study was to investigate the effect of inhibition of opioids growth pathway, in proliferation and growth of testicular germ cells and spermatogenesis following experimental diabetes in adult mice.

Material and methods: Diabetes was induced in adult mice by Streptozotocin. Diabetic animals were treated with Naltrexone 15, 30 and 60 mg/kg for 60 days. At the end of the study, testicular and body weight was recorded, tissue samples were collected and histomorphometrical studies were performed under light microscope.

Results: The results showed that the use of naltrexone has a little effect on preventing diabetic weight loss. Histomorphometric indices such as tubular diameter and germinal epithelium height were improved dose dependently in naltrexone treated diabetic mice. The number of tubular germ cells was increased non-significantly in diabetic animals following administration of naltrexone. Improvement of microscopic indices of spermatogenesis was observed in naltrexone treated diabetic mice.

Conclusions: According to the results of this study and the role of naltrexone as OGF-OGF receptor inhibitor and up-regulating activity of naltrexone which leads to increased DNA synthesis and cell division process, the administration of naltrexone could be effective in reduction of diabetic induced alterations of spermatogenesis.

Impact of Opioid and Nonopioid Drugs on Postsurgical Pain Management in the Rat

Aim. Nonsteroidal anti-inflammatory drugs or opioids are commonly used to control surgical pain following veterinary and clinical procedures. This study evaluated the efficacy of postoperative ketorolac or buprenorphine following abdominal surgery. Main Methods. Mean arterial pressure (MAP), heart rate, animal activity, corticosterone levels, and a nociceptive sensitivity assay were used to evaluate 18 adult male Sprague-Dawley rats which underwent aortic artery occlusion for implantation of a radiotelemetry device. The animals were treated postoperatively with intraperitoneal injections of vehicle, ketorolac (10 mg/kg), or buprenorphine (0.06 mg/kg) every 8 hours for 3 days. Key Findings. There were no consistent significant changes in any of the telemetry parameters after treatment with ketorolac compared with no saline treatment with the exception of increased MAP in the buprenorphine group during the first 48 hours when compared with other treatment groups. There was a sustained increase in fecal corticosterone levels from baseline on days 2–7 with buprenorphine compared with vehicle- or ketorolac-treated animals. All treatment conditions displayed reduced paw withdrawal thresholds (PWTs) from day 1 to day 21 following surgery. Compared with the vehicle treatment group, buprenorphine-treated animals exhibited significantly lower PWT levels from day 4 to 14 days. Significance. Given the prolonged increase in fecal corticosterone levels and pronounced changes in tactile hyperalgesia behavior in rodents subjected to buprenorphine treatment, these data suggest that ketorolac may be superior to buprenorphine for the treatment of postprocedure pain behavior in rodents.

Topical naltrexone accelerates full-thickness wound closure in type 1 diabetic rats by stimulating angiogenesis

Delays in wound healing often result in infection, chronic ulceration, and possible amputation of extremities. Impaired wound healing is a major complication of the 23 million people in the USA with diabetes, and financial and medical burdens are demanding new treatments for wound healing. Previous studies have demonstrated that topical application of the opioid antagonist naltrexone (NTX) dissolved in moisturizing cream reverses delays in wound closure in rats with streptozotocin-induced type 1 diabetes. A target of NTX's action is DNA synthesis and cell proliferation. In this study, granulation tissue was evaluated to ascertain the specific cellular targets that were impaired in diabetic wounds, as well as those that were enhanced following NTX application. Mast cell number as well as the number of new blood vessels immunoreactive to fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), and alpha smooth muscle actin (α-SMA) antibodies were recorded at 3, 5, 8, 10, 15, and 20 days following creation of full-thickness dorsal cutaneous wounds in normal and type 1 diabetic rats. Diabetic rats displayed delays in wound closure as well as a reduction in the number of mast cells responding to the injury, and delays in the spatial and temporal expression of FGF-2, VEGF, and α-SMA in capillaries. Topical NTX accelerated the rate of wound closure and stimulated expression of angiogenic factors within granulation tissue of diabetic rats relative to control animals receiving saline in moisturizing cream. These data support observations that a novel biological pathway is impaired under diabetic conditions and can be modulated by topical NTX to enhance proliferative events in wound healing.

The opioid growth factor-opioid growth factor receptor axis: homeostatic regulator of cell proliferation and its implications for health and disease

The opioid growth factor (OGF), chemically termed [Met(5)]-enkephalin, is an endogenous opioid peptide that interacts with the OGF receptor (OGFr) to delay the G(1)/S interface of the cell cycle by modulating cyclin-dependent inhibitory kinase (CKI) pathways. The OGF-OGFr axis is a tonically active, inhibitory pathway that is an important regulator during homeostasis and re-epithelialization, and plays a role in the onset and progression of autoimmune diseases and cancer. Modulation of the OGF-OGFr axis can be accomplished by a variety of pharmacological and molecular approaches including use of intermittent or continuous exposure to the opioid antagonist naltrexone, genetic manipulation of OGFr expression, and antibody neutralization of OGF. Clinically, OGF is a biological therapy that has potential application for treatment of cancer. Currently, naltrexone at low dosages is being evaluated for treatment of autoimmune diseases such as Crohn's and multiple sclerosis. High dosages of naltrexone are effective in reversing dry eye and accelerating the repair of corneal abrasions in normal and diabetic rats; these studies are under investigation in the clinical setting. Naltrexone also enhances full-thickness wound closure in animal models of Type 1 or Type 2 diabetes, and translation of this knowledge to the clinic is planned. In summary, understanding the OGF-OGFr axis as a homeostatic regulator of proliferation has substantial implications for maintaining human health and treatment of disease.

Diabetic keratopathy and treatment by modulation of the opioid growth factor (OGF)-OGF receptor (OGFr) axis with naltrexone: a review

The opioid growth factor (OGF)-OGF receptors (OGFr) axis plays an important role in the homeostasis and re-epithelialization of the mammalian cornea. This tonically active growth regulatory inhibitory pathway is involved in cell replication, and the endogenous neuropeptide OGF targets cyclin-dependent kinase inhibitors, p16 and/or p21. Blockade of OGF-OGFr interfacing by systemic or topical administration of opioid antagonists such as naltrexone (NTX) results in accelerated DNA synthesis, cell replication, and tissue repair. Molecular manipulation of OGFr using sense constructs delayed corneal re-epithelialization, whereas antisense constructs accelerated repair of the corneal surface. Corneal keratopathy, a significant complication of diabetes mellitus, is manifested by delays in corneal re-epithelialization following surgery, injury, or disease. Tissue culture studies have shown that addition of NTX stimulates DNA synthesis and explant outgrowth of rabbit corneal epithelium, whereas OGF depresses DNA synthesis and explant outgrowth in a receptor-mediated manner. NTX accelerated corneal re-epithelialization in organ cultures of human and rabbit cornea. Systemic application of NTX to the abraded corneas of rats, and topical administration of NTX to the injured rabbit ocular surface, increased re-epithelialization. Systemic injections or topical administration of NTX facilitates re-epithelialization of the cornea in diabetic rats. Given the vital role of the corneal epithelium in maintaining vision, the frequency of corneal complications related to diabetes (diabetic keratopathy), and the problems occurring in diabetic individuals postoperatively (e.g., vitrectomy), and that conventional therapies such as artificial tears and bandage contact lenses often fail, topical application of NTX merits clinical consideration.

The analgesic effect of morphine on postoperative pain in diabetic patients

BACKGROUND

Many clinical and experimental studies have suggested that diabetes or hyperglycemia alter opioid responsiveness. However, little information is available on the effects of diabetes mellitus on opioid requirements in the postoperative period.

METHODS

Sixty-four patients scheduled for elective, total abdominal hysterectomy were included into this prospective study to evaluate the effect of diabetes mellitus on morphine requirement in the postoperative period. A loading dose of morphine (50 micro g kg(-1)) was administered in the perioperative period. Postoperative analgesia consisted of intravenous morphine-PCA. No analgesic other than morphine was allowed during the study. In cases of inadequate analgesia intravenous 1 mg of morphine was given as a rescue analgesic. Cumulative morphine consumption, pain scores and morphine-related adverse effects were recorded.

RESULTS

A total of 60 patients were evaluated: Group D, 30; and Group ND, 30. Patients in Group D received more morphine than those in Group ND (54.12 +/- 25.09 and 42.66 +/- 20.67, respectively). The difference in cumulative morphine consumption was higher in the first hour (P = 0.037) in diabetic patients and they required significantly more morphine in the last 24 h (P = 0.015). Postoperative pain scores were higher in the diabetic group. More patients in the diabetic group required rescue medication (26 vs. 19) and felt nauseous (25 vs. 14; P = 0.003).

CONCLUSION

The findings of the study appear to support experimental and clinical impressions that the analgesic effect of morphine is attenuated in hyperglycemic conditions. Therefore, larger doses of morphine may be administered to diabetic patients for effective postoperative analgesia.

Animal and cellular models of chronic pain

Chronic pain, especially neuropathic pain and cancer pain, is often not adequately treated by currently available analgesics. Animal models provide pivotal systems for preclinical study of pain. This article reviews some of the most widely used or promising new models for chronic pain. Partial spinal ligation, chronic constriction injury, and L5/L6 spinal nerve ligation represent three of the best characterized rodent models of peripheral neuropathy. Recently, several mouse and rat bone cancer pain models have been reported. Primary or permanent cultures of sensory neurons have been established to study the molecular mechanism of pain, especially for neurotransmitter release and signal transduction. The emerging gene microarray, genomics and proteomics methods may be applied to throughly characterize these cells. Each model is uniquely created with distinct mechanisms, it is therefore essential to report and interpret results in the context of a specific model.

Diabetic neuropathy: inhibitory G protein dysfunction involves PKC-dependent phosphorylation of Goalpha

We examined the hypothesis that decreased inhibitory G protein function in diabetic neuropathy is associated with increased protein kinase C (PKC)-dependent phosphorylation of the Goalpha subunit. Streptozotocin-induced diabetic rats were studied between 4 and 8 weeks after onset of diabetes and compared with aged-matched healthy animals as controls. Opioid-mediated inhibition of forskolin-stimulated cyclic AMP was significantly less in dorsal root ganglia (DRGs) from diabetic rats compared with controls. Activation of PKC in DRGs from control rats was associated with a significant decrease in opioid-mediated inhibition of forskolin-stimulated cyclic AMP that was similar to the decrease in inhibition observed in DRGs from diabetic rats. Both basal and PKC-mediated labeling of Goalpha with 32Pi was significantly less in DRGs from diabetic rats, supporting increased endogenous PKC-dependent phosphorylation of Goalpha. Probing of immunoprecipitated Goalpha with an anti-phospho-serine/threonine specific antibody revealed a significant increase in baseline phosphorylation in diabetic DRGs. Activation of PKC produced a significant increase in phosphorylation in control DRGs but no significant increase in Goalpha in diabetic DRGs. Phosphorylation of PKC-alpha was increased, PKC-betaII was unchanged and PKC-delta decreased in diabetic DRGs. These results suggest that diminished inhibitory G protein function observed in DRGs neurons from diabetic rats involves an isoform-specific PKC-dependent pathway.

Naltrexone, an opioid antagonist, facilitates reepithelialization of the cornea in diabetic rat

Ulcers and erosions of the corneal epithelium, as well as delays in resurfacing of the cornea after wounding, are major causes of ocular morbidity and visual loss in diabetes. To study whether intervention by the opioid antagonist naltrexone (NTX; 30 mg/kg, twice daily) can restore reepithelialization in diabetic cornea, we induced diabetes in rats by intravenous injection of 65 mg/kg streptozotocin. After confirmation of diabetes, 5-mm-diameter epithelial defects that did not include the limbus were created by mechanical scraping of the cornea. At 4 and 8 weeks, corneal reepithelialization was markedly subnormal, with delays ranging from 11% to 17-fold in the diabetic animals compared with control counterparts. Rats that were diabetic for 8 weeks also had a significant decrease in the incidence of complete wound closure. At 4 and 8 weeks, diabetic animals that were receiving NTX had an acceleration in reepithelialization compared with diabetic animals that were receiving vehicle and even surpassed controls. DNA synthesis in the corneal epithelium of diabetic rats was decreased up to 90% of control levels, and NTX exposure of diabetic subjects elevated the labeling index by up to eightfold from diabetic animals that were receiving vehicle. Opioid growth factor and opioid growth factor receptor distribution were comparable in diabetic and control animals. These results indicate a delay in reepithelialization that is dependent on the duration of diabetes and that intervention of endogenous opioid-receptor interfacing with an opioid antagonist can facilitate the process of wound healing.

Altered meiotic regulation in oocytes from diabetic mice

In the present study, we have utilized a streptozotocin-induced diabetic mouse model to examine how the diabetic condition and different glucose concentrations affect several parameters of reproductive physiology. We report that oocyte maturation is altered under all experimental conditions examined. In cumulus cell-enclosed oocytes (CEO) from diabetic mice, spontaneous maturation was accelerated but the FSH-mediated delay of spontaneous maturation was suppressed. Higher glucose levels in the culture medium suppressed spontaneous maturation but did not influence the transient arrest mediated by FSH. Meiotic arrest in CEO by hypoxanthine and dibutyryl cAMP (dbcAMP) was less effective at higher glucose concentrations. In addition, both FSH-induced maturation in vitro and hCG-induced maturation in vivo were reduced by the diabetic condition. The ovulation rate was lowered by about 50% in diabetic mice and fewer ovulated ova had reached metaphase II. Despite the decreased number of ova at metaphase II, in vitro cultures showed the oocytes were capable of completing meiotic maturation at control levels. Insulin treatment reversed the detrimental effects of diabetes on meiotic induction, ovulation, and completion of meiotic maturation. Cultures of pronuclear-staged embryos confirmed a negative effect of diabetes and hyperglycemia on development to the blastocyst stage. These data suggest that defects in meiotic regulation brought about by the diabetic condition are due to decreased communication between the somatic and germ cell compartments, and it is concluded that such conditions may contribute to postfertilization developmental abnormalities.

Role of L-type Ca2+ channels in attenuated morphine antinociception in streptozotocin-diabetic rats

The role of L-type Ca2+ channels in morphine antinociception was studied in streptozotocin-induced diabetic and control rats, using [3H]PN200-110 [isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-methoxycabonylpyridine-3-caboxylate] binding (0.005-1.0 nmol/l) and rat whole brain membranes, to determine if the attenuation of morphine antinociception was related to alterations in dihydropyridine-sensitive Ca2+ channel binding characteristics. The tail-flick antinociceptive effect of morphine (4 mg/kg, i.p.) was significantly reduced in diabetic rats in comparison to that in controls. Nimodipine (0.1-3 mg/kg, i.p.) did not produce antinociception but significantly potentiated the morphine response in control rats. Nimodipine (0.3-3 mg/kg, i.p.) reversed the attenuation of morphine antinociception in a dose-dependent manner in diabetic rats. Moreover, insulin (2 U/kg, s.c.) [correction of mu/kg] reversed the attenuated morphine antinociception in streptozotocin-diabetic rats. A significant increase in the Bmax (+41%) of [3H]PN200-110 binding was observed in diabetic rat brain membranes compared to that in control rats. However, there was no change in affinity (Kd) value of [3H]PN200-110. The reduced morphine response in diabetic rats, in accordance with up-regulation of dihydropyridine sites, may be due to an increased Ca2+ influx through L-type channels. These results suggest a functional role of L-type Ca2+ channels in morphine antinociception and the diabetic state may lead to alterations in their density.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.