Fear learning circuitry is biased toward generalization of fear associations in posttraumatic stress disorder

Fear conditioning is an established model for investigating posttraumatic stress disorder (PTSD). However, symptom triggers may vaguely resemble the initial traumatic event, differing on a variety of sensory and affective dimensions. We extended the fear-conditioning model to assess generalization of conditioned fear on fear processing neurocircuitry in PTSD. Military veterans (n=67) consisting of PTSD (n=32) and trauma-exposed comparison (n=35) groups underwent functional magnetic resonance imaging during fear conditioning to a low fear-expressing face while a neutral face was explicitly unreinforced. Stimuli that varied along a neutral-to-fearful continuum were presented before conditioning to assess baseline responses, and after conditioning to assess experience-dependent changes in neural activity. Compared with trauma-exposed controls, PTSD patients exhibited greater post-study memory distortion of the fear-conditioned stimulus toward the stimulus expressing the highest fear intensity. PTSD patients exhibited biased neural activation toward high-intensity stimuli in fusiform gyrus (P<0.02), insula (P<0.001), primary visual cortex (P<0.05), locus coeruleus (P<0.04), thalamus (P<0.01), and at the trend level in inferior frontal gyrus (P=0.07). All regions except fusiform were moderated by childhood trauma. Amygdala–calcarine (P=0.01) and amygdala–thalamus (P=0.06) functional connectivity selectively increased in PTSD patients for high-intensity stimuli after conditioning. In contrast, amygdala–ventromedial prefrontal cortex (P=0.04) connectivity selectively increased in trauma-exposed controls compared with PTSD patients for low-intensity stimuli after conditioning, representing safety learning. In summary, fear generalization in PTSD is biased toward stimuli with higher emotional intensity than the original conditioned-fear stimulus. Functional brain differences provide a putative neurobiological model for fear generalization whereby PTSD symptoms are triggered by threat cues that merely resemble the index trauma.     

An alternative extrinsic pathway of human blood coagulation

To study the interrelationships of the major human coagulation pathways, factor X activation in normal and various deficient human plasmas was evaluated when clotting was triggered by dilute rabbit or human thromboplastin. Various dilutions of thromboplastin were added to plasma samples containing 3H-labeled factor X, and the time course of factor X activation was determined. At a 1/250 dilution of rabbit brain thromboplastin the rate of factor X activation in factor VIII or factor IX deficient plasma was only 10% of the activation rate seen for normal or factor XI deficient plasma. Reconstitution of the deficient plasmas with factors VIII or IX, respectively, restored normal factor X activation. Similar results were obtained when various dilutions of human thromboplastin replaced the rabbit thromboplastin. From these experiments, it is inferred that normal activation of factor X in plasma due to dilute thromboplastin requires factors VII, IX and VIII. An alternative extrinsic pathway that involves factors VII, IX, and VIII may be a major physiologic extrinsic pathway, and this pathway may help to explain the clinical observations of bleeding diatheses in patients deficient in factors IX or VIII.     

Establishing and managing a periodontal biobank for research: the sharing of experience

Periodontal bio‐repositories, which allow banking of clinically validated human data and biological samples, provide an opportunity to derive biomarkers for periodontal diagnosis, prognosis and therapeutic activities which are expected to improve patient management. This article presents the establishing of the Malaysian Periodontal Database and Biobank System (MPDBS) which was initiated in 2011 with the aim to facilitate periodontal research. Partnerships were established with collaborating centres. Policies on specimen access, authorship and acknowledgement policies were agreed upon by all participating centres before the initiation of the periodontal biobank. Ethical approval for the collection of samples and data were obtained from institutional ethics review boards. A broad‐based approach for informed consent was used, which covered areas related to quality of life impacts, genetics and molecular aspects of periodontal disease. Sample collection and processing was performed using a standardized protocol. Biobanking resources such as equipment and freezers were shared with the Malaysian Oral Cancer Database and Tissue Bank System (MOCDTBS). In the development of the MPDBS, challenges that were previously faced by the MOCDTBS were considered. Future challenges in terms of ethical and legal issues will be faced when international collaborations necessitate the transportation of specimens across borders.     

Cardiovascular protection with sodium-glucose co-transporter-2 inhibitors in type 2 diabetes: Does it apply to all patients?

Patients with type 2 diabetes (T2D) are at an increased risk of cardiovascular disease (CVD). Cardiovascular risk in these patients should be considered as a continuum, and comprehensive treatment strategies should aim to target multiple disease risk factors. Large-scale clinical trials of sodium-glucose co-transporter-2 (SGLT2) inhibitors have shown an impact on cardiovascular outcomes, including heart failure hospitalization and cardiovascular death, which appears to be independent of their glucose-lowering efficacy. Reductions in major cardiovascular events appear to be greatest in patients with established CVD, particularly those with prior myocardial infarction, but are independent of heart failure or renal risk. Most large-scale trials of SGLT2 inhibitors predominantly include patients with T2D with pre-existing CVD and high cardiovascular risk at baseline, limiting their applicability to patients typically observed in clinical practice. Real-world evidence from observational studies suggests that there might also be beneficial effects of SGLT2 inhibitors on heart failure hospitalization and all-cause mortality in various cohorts of lower risk patients. The most common adverse events reported in clinical and observational studies are genital infections; however, the overall risk of these events appears to be low and easily managed. Similar safety profiles have been reported for elderly and younger patients. There is still some debate regarding the safety of canagliflozin in patients at high risk of fracture and amputation. Outstanding questions include specific patterns of cardiovascular protection according to baseline risk.     

Insulin use in elderly adults: risk of hypoglycemia and strategies for care

Hypoglycemia is a significant problem in elderly adults with diabetes mellitus. Elderly individuals with diabetes mellitus are at greater risk than younger adults for hypoglycemic events. Several factors contribute to this risk, including the high prevalence of comorbidities, polypharmacy, cognitive impairment, and concomitant use of agents that interfere with glucose metabolism. To minimize the risk of hypoglycemia and maximize the benefits of glycemic control, guidelines typically recommend individualizing glycosylated hemoglobin (HbA1c) targets based on life expectancy, functional status, and individual goals. Although many individuals with type 2 diabetes mellitus will ultimately require insulin therapy to achieve and maintain glycemic control, earlier insulin initiation in elderly individuals may be warranted, particularly in those with renal, cardiovascular, or hepatic concerns that could interfere with the use of oral agents. There are few data on the use of insulin-or other glucose-lowering agents-in elderly adults, but limited evidence suggests that the use of insulin, especially insulin analogs, may be appropriate in this population. Insulin analogs offer a better pharmacokinetic profile, greater convenience, and less variable glycemic control than human insulin. Because of the high prevalence of cognitive impairment and other geriatric syndromes in elderly adults, clinicians should perform a comprehensive assessment of patients' ability to administer and monitor insulin therapy and recognize and treat hypoglycemia.