CRF serum levels differentiate PTSD from healthy controls and TBI in military veterans

Background and Objective

Posttraumatic stress disorder (PTSD) is a serious and frequently debilitating psychiatric condition that can occur in people who have experienced traumatic stressors, such as war, violence, sexual assault and other life‐threatening events. Treatment of PTSD and traumatic brain injury (TBI) in veterans is challenged by diagnostic complexity, partially due to PTSD and TBI symptoms overlap and to the fact that subjective self‐report assessments may be influenced by a patient's willingness to share their traumatic experiences and resulting symptoms. Corticotropin‐releasing factor (CRF) is one of the main mediators of hypothalamic pituitary adrenal (HPA)‐axis responses in stress and anxiety.

Methods and Results

We analyzed serum CRF levels in 230 participants including heathy controls (64), and individuals with PTSD (53), TBI (70) or PTSD + TBI (43) by enzyme immunoassay (EIA). Significantly lower CRF levels were found in both the PTSD and PTSD + TBI groups compared to healthy control (PTSD vs. Controls: P = 0.0014, PTSD + TBI vs. Controls: P = 0.0011) and chronic TBI participants (PTSD vs. TBI: P < 0.0001, PTSD + TBI vs. TBI: P < 0.0001), suggesting a PTSD‐related mechanism independent from TBI and associated with CRF reduction. CRF levels negatively correlated with PTSD severity on the Clinically Administered PTSD Scale (CAPS‐5) scale in the whole study group.

Conclusions

Hyperactivation of the HPA axis has been classically identified in acute stress. However, the recognized enhanced feedback inhibition of the HPA axis in chronic stress supports our findings of lower CRF in PTSD patients. This study suggests that reduced serum CRF in PTSD should be further investigated. Future validation studies will establish if CRF is a possible blood biomarker for PTSD and/or for differentiating PTSD and chronic TBI symptomatology.

The HPA axis is activated under acute stress conditions, but an enhanced feedback inhibition may be prevalent in chronic stress conditions such as PTSD.

We observed a reduction in serum CRF levels in veterans with PTSD and PTSD + TBI, but not in veterans with chronic TBI alone.

A serum CRF reduction may be indicative of CNS mechanisms specific to PTSD and should be further evaluated as a possible peripheral biomarker.

Utilization of machine learning for identifying symptom severity military-related PTSD subtypes and their biological correlates

We sought to find clinical subtypes of posttraumatic stress disorder (PTSD) in veterans 6-10 years post-trauma exposure based on current symptom assessments and to examine whether blood biomarkers could differentiate them. Samples were males deployed to Iraq and Afghanistan studied by the PTSD Systems Biology Consortium: a discovery sample of 74 PTSD cases and 71 healthy controls (HC), and a validation sample of 26 PTSD cases and 36 HC. A machine learning method, random forests (RF), in conjunction with a clustering method, partitioning around medoids, were used to identify subtypes derived from 16 self-report and clinician assessment scales, including the clinician-administered PTSD scale for DSM-IV (CAPS). Two subtypes were identified, designated S1 and S2, differing on mean current CAPS total scores: S2 = 75.6 (sd 14.6) and S1 = 54.3 (sd 6.6). S2 had greater symptom severity scores than both S1 and HC on all scale items. The mean first principal component score derived from clinical summary scales was three times higher in S2 than in S1. Distinct RFs were grown to classify S1 and S2 vs. HCs and vs. each other on multi-omic blood markers feature classes of current medical comorbidities, neurocognitive functioning, demographics, pre-military trauma, and psychiatric history. Among these classes, in each RF intergroup comparison of S1, S2, and HC, multi-omic biomarkers yielded the highest AUC-ROCs (0.819-0.922); other classes added little to further discrimination of the subtypes. Among the top five biomarkers in each of these RFs were methylation, micro RNA, and lactate markers, suggesting their biological role in symptom severity.

Vial breakage during freeze‐drying: Crystallization of sodium chloride in sodium chloride‐sucrose frozen aqueous solutions

The purpose of this study was to evaluate sodium chloride-sucrose frozen solutions with regard to sodium chloride crystallization and vial strain. Sodium chloride-sucrose solutions were studied using Differential Scanning Calorimetry (DSC) and a strain gauge instrumented vial. The sodium chloride concentration was varied with a fixed concentration of sucrose to identify a composition where crystallization was observed during heating and this composition was examined using the strain-gauged vials. DSC heating thermograms of a 1:1 (w/w) ratio of sodium chloride-sucrose solution show a sodium chloride crystallization exotherm at approximately -45 degrees C. Examination of this composition in a strain-gauged vial shows an increase in strain, which corresponds to the temperature of the exotherm. Vial breakage is a phenomenon reported for mannitol containing solutions, which is associated with crystallization of mannitol in frozen solution. These data also suggest that vial strain and breakage is associated with the crystallization of solutes and the crystallization of water, which is released from the amorphous phase to form ice, and volume expansion. The results demonstrate the importance of understanding effect of excipient ratios, specifically in systems containing crystallizing and non-crystallizing excipients, and thermal history when developing freeze-dried formulations.

Existence of a mannitol hydrate during freeze-drying and practical implications

We report thermal and crystallographic evidence for a previously unknown mannitol hydrate that is formed in the process of freeze-drying. The mannitol hydrate was produced by freeze-drying pure mannitol solutions (1-4% w/v) using the following cycle: (1) equilibration at -5 degreesC for 1 h; (2) freezing at -40 degreesC; (3) primary drying at -10 degreesC for 15 h; and (4) secondary drying at 10 degreesC for 2 h and then 25 degreesC for 5 h. This crystal form was also observed upon freeze-drying in the presence of sorbitol (1% w/v). The mannitol hydrate showed a distinct X-ray powder diffraction pattern, low melting point, and steplike desolvation behavior that is characteristic of crystalline hydrates. The mannitol hydrate was found to be metastable, converting to anhydrous polymorphs of mannitol upon heating and exposure to moisture. The amount of the mannitol hydrate varied significantly from vial to vial, even within the same batch. The formation of mannitol hydrate has several potential consequences: (1) reduced drying rate; (2) redistribution of the residual hydrate water during accelerated storage to the amorphous drug; and (3) vial-to-vial variation of the moisture level.

Evaluation of manometric temperature measurement as a method of monitoring product temperature during lyophilization

The objective of this study was to evaluate manometric temperature measurement as a non-invasive method of monitoring product temperature during the primary drying phase of lyophilization. This method is based on analysis of the transient response of the chamber pressure when the flow of water vapor from the chamber to the condenser is momentarily interrupted. Manometric temperature measurements (MTM) were compared to product temperature data measured by thermocouples during the lyophilization of water, mannitol, lactose and potassium chloride solutions. The transient pressure response was mathematically modeled by assuming that four mechanisms contribute to the pressure rise: 1) direct sublimation of ice through the dried product layer at a constant temperature, 2) an increase in the temperature at the sublimation interface due to equilibration of the temperature gradient across the frozen layer, 3) an increase in the ice temperature due to continued heating of the frozen matrix during the measurement, and 4) leaks in the chamber. Experimental transient pressure response data were fitted to an equation consisting of the sum of these terms containing three variables corresponding to the vapor pressure of ice, product resistance to vapor flow, and the vial heat transfer coefficient. Excellent fit between the mathematical model and the experimental data was observed, and the value of the variables was calculated from the measured transient pressure response by a least squares method. The product temperature measured by MTM, which measures the temperature at the sublimation interface, was compared with product temperature measured by thermocouples placed in the bottom center of the vials. Manometrically measured temperatures were consistently lower than the thermocouple measurements by about 2 degrees C, this difference being largely accounted for by the temperature gradient across the frozen layer. The resistance of the dried product to mass transfer calculated from MTM was found to agree reasonably well with values measured by a direct vial technique. Product resistance was observed to increase with increasing solute concentration, and to increase continuously as the depth of the dried product layer increases for mannitol and potassium chloride. For lactose, product resistance increases continuously with thickness up to the onset of collapse, at which point the product resistance becomes essentially independent of depth. Scanning electron microscopy was used to explain this observation based on changes in morphology of the solid. The vial heat transfer coefficients obtained from regression analysis were on the order of 10(-3)-10(-4) cal.sec-1. degrees C-1; however, the scatter in the vial heat transfer coefficient data prevents the method from being used for accurate measurement of the vial heat transfer coefficient. The results of the study show that the manometric method shows promise as a process development tool and as an alternative method of in-process product temperature measurement during primary drying.

The physical state of nafcillin sodium in frozen aqueous solutions and freeze-dried powders

The purpose of this study was to develop a better understanding of the physical chemistry of freeze drying of lyotropic liquid crystals using nafcillin sodium as a model solute. Solutions and freeze-dried powders of nafcillin sodium were studied by polarized light microscopy, differential scanning calorimetry, x-ray powder diffraction, and water vapor adsorption. Differential scanning calorimetry thermograms of nafcillin sodium solutions contain a melting endotherm at approximately -5.5 degrees C and, depending on the concentration and heating rate, a crystallization exotherm immediately after this endotherm followed by the melting endotherm of ice. When the sample is annealed at -4 degrees C, both the endotherm and exotherm are eliminated, and a new endotherm appears at approximately -1 degree C on the shoulder of the ice-melting endotherm. The data are interpreted as melting of a liquid crystalline phase, followed by crystallization. X-ray powder diffractograms of unannealed freeze-dried nafcillin sodium are consistent with a lamellar liquid crystal. Diffractograms of annealed freeze-dried nafcillin sodium indicate crystalline material which is a different crystal form than the monohydrate starting material. Moisture adsorption isotherms of the freeze-dried annealed (crystalline) and unannealed (liquid crystalline) nafcillin sodium show different affinities for moisture compared to the crystalline starting material. Solid-state stability data demonstrate that the freeze-dried liquid crystalline form of nafcillin sodium is much less stable than the freeze-dried crystal-line material. The literature recognizes two types of solute behavior on freezing, where the solute either crystallizes from the freeze concentrate or remains amorphous. Lyotropic liquid crystal formation during freezing represents a separate category of freezing behavior, the physical chemistry of which is worthy of further investigation.

Glycine crystallization during freezing: the effects of salt form, pH, and ionic strength

PURPOSE

The purpose of the study is to characterize glycine crystallization during freezing of aqueous solutions as a function of the glycine salt form (i.e., neutral glycine, glycine hydrochloride, and sodium glycinate), pH, and ionic strength.

METHODS

Crystallization was studied by thermal analysis, microscopy, x-ray diffraction, and pulsed Fourier transform nmr spectroscopy.

RESULTS

A solution of neutral glycine with no additives undergoes rapid secondary crystallization during freezing, forming the beta polymorph, with a eutectic melting temperature of -3.4 degrees C. Glycine hydrochloride solutions undergo secondary crystallization relatively slowly, and the eutectic melting temperature is -28 degrees C. Sodium glycinate crystallizes from frozen solution at an intermediate rate, forming a eutectic mixture with a melting temperature of -17.8 degrees C. Where secondary crystallization does not occur rapidly, a complex glass transition is observed in the -70 degrees to -85 degrees C temperature range in the DSC thermograms of all systems studied. Rates of secondary crystallization and the type of crystal formed are influenced by solution pH relative the the pKs of glycine, and also by the change in ionic strength caused by adjustment of pH. Increased ionic strength significantly slows the crystallization of neutral glycine and promotes formation of the gamma polymorph. Thermal treatment or extended holding times during the freezing process may be necessary in order to promote secondary crystallization and prevent collapse during freeze drying.

CONCLUSIONS

The results underscore the importance of recognizing that seemingly minor changes in formulation conditions can have profound effects on the physical chemistry of freezing and freeze drying.

The effect of bulking agent on the solid-state stability of freeze-dried methylprednisolone sodium succinate

The rate of hydrolysis of methylprednisolone sodium succinate in the freeze dried solid state at 40 degrees C was determined in the presence of two common bulking agents--mannitol and lactose--at two different ratios of drug to excipient. Residual moisture levels were less than 1% in all samples tested, with no significant difference in residual moisture among different formulations. Rate of hydrolysis was significantly higher in mannitol-containing formulations versus lactose-containing formulations, and the rate of hydrolysis increases with increasing ratio of mannitol to drug. Thermal analysis and x-ray diffraction data are consistent with a composition-dependent rate of crystallization of mannitol in the formulation and its subsequent effect on distribution of water in the freeze-dried matrix. Increased water in the microenvironment of the drug decreases the glass transition temperature of the amorphous phase, resulting in an increased rate of reaction. The physical state of lactose remained constant throughout the duration of the study, and the rate of hydrolysis was not significantly different from the control formulation containing no excipient. Thermal analysis and x-ray diffraction data are consistent with formation of a liquid crystal phase in freeze-concentrated solutions of methylprednisolone sodium succinate containing no excipient.

Measurement of excessive appetite and metabolic changes in Prader-Willi syndrome

The behavioural, cognitive and metabolic response to food intake was studied in 13 adults with the Prader-Willi syndrome (PWS) and compared to ten age-matched controls. Rates of eating were observed during one hour's access to food and feelings of hunger were assessed using a visual analogue scale. Blood was taken for estimation of glucose, insulin, cholecystokinin (CCK), prolactin, growth hormone (GH) and cortisol every 20 min for a total period of 100 min. Ten (76%) of the subjects with PWS ate steadily for the whole hour that food was available and on average consumed three times more calories than the control group. The median ratings for feelings of hunger in the PWS group changed in the expected direction but these changes were delayed compared to the control group and only reached the same level as the controls after the PWS subjects had eaten a significantly greater amount of food. In the PWS group, in contrast to the control group, feelings of hunger started to re-emerge shortly after food was removed. There were marked differences between individuals with PWS in the extent of the changes in serum prolactin levels. Increases in plasma glucose levels were inversely correlated with changes in hunger ratings in the PWS group, but not the control group. There was a significantly greater increase in serum CCK levels during the meal in the PWS group than in the control group indicating that in PWS failure of peripheral release of CCK in response to food intake was not the explanation for the impaired satiety response.