Insulin resistance is a homeorhetic adaptation to parturition in dairy cows transitioning from late pregnancy to early lactation. An increase in prepartum adiposity can predispose periparturient cows to greater lipolysis and insulin resistance, thus increasing the risk for metabolic disease. Mechanisms mediating the development of insulin resistance in overweight peripartal dairy cows may depend on ceramide metabolism. The sphingolipid ceramide accumulates in plasma and tissues of overweight monogastric animals, and facilitates saturated fatty acid-induced insulin resistance. Considering this evidence, we hypothesized that plasma ceramides would be elevated in periparturient dairy cattle and that these sphingolipids would correlate with the magnitude of lipolysis and insulin resistance. To test our central hypothesis, multiparous Holstein cows were allocated into 2 groups according to their body condition score (BCS) at d −30 prepartum: lean (BCS <3.0; n = 10) or overweight (BCS >4.0; n = 11). Blood samples were collected at d −45, −30, −15, and −7, relative to expected parturition, and at d 4 postpartum. Plasma glucose, insulin, nonesterified fatty acids (NEFA), and β-hydroxybutyrate (BHBA) concentrations were measured, and insulin sensitivity was estimated. The concentrations of individual plasma ceramide and glycosylated ceramide were determined using liquid chromatography-based mass spectrometry. Results demonstrated that greater adiposity was associated with a greater loss in body condition during late pregnancy. Overweight cows had greater circulating concentrations of glucose, insulin, and NEFA, and lower insulin sensitivity relative to lean cows. We detected 30 different sphingolipids across 6 lipid classes with acyl chains ranging from 16 to 26 carbons. The most abundant plasma sphingolipids detected were C24:0-ceramide, C24:0-monohexosylceramide, and C16:0-lactosylceramide. Plasma concentrations of total ceramide and monohexosylceramide increased as lactation approached, and saturated ceramide and monohexosylceramide were elevated in cows with greater adiposity relative to those with a lean phenotype. Plasma ceramides (e.g., C24:0-ceramide) were positively correlated with plasma NEFA and inversely correlated with insulin sensitivity. Our data demonstrate a remodeled plasma sphingolipidome in dairy cows transitioning from late pregnancy to lactation characterized by a concomitant increase in plasma ceramides with the development of peripartal insulin resistance.

Ceramide is a bioactive lipid that plays an important role in stress responses leading to apoptosis, cell growth arrest and differentiation. Ceramide production is due in part to sphingomyelin hydrolysis by sphingomyelinases. In brain, neutral sphingomyelinase 2 (nSMase2) is expressed in neurons and increases in its activity and expression have been associated with pro-inflammatory conditions observed in Alzheimer’s disease, multiple sclerosis and human immunodeficiency virus (HIV-1) patients. Increased nSMase2 activity translates into higher ceramide levels and neuronal cell death, which can be prevented by chemical or genetic inhibition of nSMase2 activity or expression. However, to date, there are no soluble, specific and potent small molecule inhibitor tool compounds for in vivo studies or as a starting point for medicinal chemistry optimization. Moreover, the majority of the known inhibitors were identified using bacterial, bovine or rat nSMase2. In an attempt to identify new inhibitor scaffolds, two activity assays were optimized as screening platform using the recombinant human enzyme. First, active hits were identified using a fluorescence-based high throughput compatible assay. Then, hits were confirmed using a 14C sphingomyelin-based direct activity assay. Pharmacologically active compounds and approved drugs were screened using this strategy which led to the identification of cambinol as a novel uncompetitive nSMase2 inhibitor (K i = 7 μM). The inhibitory activity of cambinol for nSMase2 was approximately 10-fold more potent than for its previously known target, silence information regulator 1 and 2 (SIRT1/2). Cambinol decreased tumor necrosis factor-α or interleukin-1 β-induced increases of ceramide and cell death in primary neurons. A preliminary study of cambinol structure and activity allowed the identification of the main structural features required for nSMase2 inhibition. Cambinol and its analogs may be useful as nSMase2 inhibitor tool compounds to prevent ceramide-dependent neurodegeneration.

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When long-term memories are reactivated, they can reenter a transient plastic state in which they are vulnerable to interference or physiological manipulations. The present study attempted to directly affect reactivated memories through a stress manipulation, and compared the effects of stress on reactivated and nonreactivated components of a declarative memory in a within-subject design. We presented image pairs that consisted of an image of an animal and an image of an unrelated object. Participants were instructed to memorize the object images. Forty-eight hours later, we presented half of the animal images again in an unrelated task to indirectly reactivate the associated object images. Immediately after reactivation, participants were exposed to cold pressor stress or a warm water control condition. Forty-eight hours later, we assessed memory for the object images with a free recall test. Reactivation boosted memory performance in the control condition, such that reactivated items were better recalled than nonreactivated items. This memory-enhancing effect of reactivation was completely abolished by cold pressor stress. Importantly, stress selectively impacted only the reactivated items while leaving memory for the nonreactivated items unaffected. The present study shows that it is possible to selectively reactivate and modulate specific parts of a declarative memory.

Objective: To evaluate interictal, circulating sphingolipids in women migraineurs.Methods: In the fasting state, serum samples were obtained pain-free from 88 women with episodic migraine (EM; n 5 52) and from controls (n 5 36). Sphingolipids were detected and quantified by high-performance liquid chromatography coupled with tandem mass spectrometry using multiple reaction monitoring. Multivariate logistic regression was used to examine the association between serum sphingolipids and EM odds. A recursive partitioning decision tree based on the serum concentrations of 10 sphingolipids was used to determine the presence or absence of EM in a subset of participants.Results: Total ceramide (EM 6,502.9 ng/mL vs controls 10,518.5 ng/mL; p , 0.0001) and dihydroceramide (EM 39.3 ng/mL vs controls 63.1 ng/mL; p , 0.0001) levels were decreased in those with EM as compared with controls. Using multivariate logistic regression, each SD increase in total ceramide (odds ratio [OR] 0.07; 95% confidence interval [CI]: 0.02, 0.22; p , 0.001) and total dihydroceramide (OR 0.05; 95% CI: 0.01, 0.21; p , 0.001) levels was associated with more than 92% reduced odds of migraine. Although crude sphingomyelin levels were not different in EM compared with controls, after adjustments, every SD increase in the sphingomyelin species C18:0 (OR 4.28; 95% CI: 1.87, 9.81; p 5 0.001) and C18:1 (OR 2.93; 95% CI: 1.55, 5.54; p 5 0.001) was associated with an increased odds of migraine. Recursive portioning models correctly classified 14 of 14 randomly selected participants as EM or control. Conclusion:These results suggest that sphingolipid metabolism is altered in women with EM and that serum sphingolipid panels may have potential to differentiate EM presence or absence. Classification of evidence:This study provides Class III evidence that serum sphingolipid panels accurately distinguish women with migraine from women without migraine. Neurology ® 2015;85:1214-1223 GLOSSARY BMI 5 body mass index; C1P 5 ceramide-1-phosphate; CI 5 confidence interval; DHC 5 dihydroceramide; DHSM 5 dihydrosphingomyelin; DSM-IV 5 Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition); EM 5 episodic migraine; HIT-6 5 Headache Impact Test-6; LacCer 5 lactosylceramide; MHC 5 monohexosylceramide; OPLS-DA 5 orthogonal partial least squares discriminant analysis; OR 5 odds ratio; PHQ-9 5 Patient Health Questionnaire-9; S1P 5 sphingosine-1-phosphate; SM 5 sphingomyelin.Although the full pathophysiology of migraine is not known, current theories suggest that migraine is largely an inherited brain disorder associated with a sterile, neurogenic inflammation and alterations in neuronal excitability and the cerebrovasculature.1,2 Several lines of evidence also indicate that migraineurs have a greater risk of stroke and disorders related to lipid metabolism including hypercholesterolemia, impaired insulin sensitivity, and obesity. [3][4][5][6] Sphingolipids (e.g., sphingomyelins, ceramides) are a group of bioactive lipids that are critical components of m...