Nicotinic acids: liver-targeted SCD inhibitors with preclinical anti-diabetic efficacy

An in vitro screening protocol was used to transform a systemically-distributed SCD inhibitor into a liver-targeted compound. Incorporation of a key nicotinic acid moiety enables molecular recognition by OATP transporters, as demonstrated by uptake studies in transfected cell lines, and likely serves as a critical component of the observed liver-targeted tissue distribution profile. Preclinical anti-diabetic oGTT efficacy is demonstrated with nicotinic acid-based, liver-targeting SCD inhibitor 10, and studies with a close-structural analog devoid of SCD1 activity, suggest this efficacy is a result of on-target activity.     

The intron 7 donor splice site transition: a second Tay-Sachs disease mutation in French Canada

Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a GA transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7+1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7+1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7+1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada.     

Bicyclic heteroaryl inhibitors of stearoyl-CoA desaturase: from systemic to liver-targeting inhibitors

Optimization of a lead thiazole amide MF-152 led to the identification of potent bicyclic heteroaryl SCD1 inhibitors with good mouse pharmacokinetic profiles. In a view to target the liver for efficacy and to avoid SCD1 inhibition in the skin and eyes where adverse effects were previously observed in rodents, representative systemically-distributed SCD1 inhibitors were converted into liver-targeting SCD1 inhibitors.     

Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale

Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two–three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries.     

Compartmentalized expression of three novel sarco/endoplasmic reticulum Ca2+ATPase 3 isoforms including the switch to ER stress, SERCA3f, in non-failing and failing human heart

The human sarco/endoplasmic reticulum (ER) Ca(2+)ATPase 3 (SERCA3) gene gives rise to SERCA3a-3f isoforms, the latter inducing ER stress in vitro. Here, we first demonstrated the co-expression of SERCA3a, -3d and -3f proteins in the heart. Evidence for endogenous proteins was obtained by using isoform-specific antibodies including a new SERCA3d-specific antibody, and either Western blotting of protein lysates or immunoprecipitation of membrane proteins. An immunolocalization study of both left ventricle tissue and isolated cardiomyocytes showed a distinct compartmentalization of the SERCA3 isoforms, as a uniform distribution of SERCA3a was detected while -3d and -3f isoforms were observed around the nucleus and in close vicinity of plasma membrane, respectively. Second, we studied their expressions in failing hearts including mixed (MCM) (n=1) and idiopathic dilated (IDCM) cardiomyopathies (n=4). Compared with controls (n=5), similar expressions of SERCA3a and -3d mRNAs were observed in all patients. In contrast, SERCA3f mRNA was found to be up-regulated in failing hearts (125+/-7%). Remarkably, overexpression of SERCA3f paralleled an increase in ER stress markers including processing of X-box-binding protein-1 (XBP-1) mRNA (176+/-24%), and expression of XBP-1 protein and glucose-regulated protein (GRP)78 (232+/-21%). These findings revisit the human heart's Ca(2+)ATPase system and indicate that SERCA3f may account for the mechanism of ER stress in vivo in heart failure.     

Neurons containing gastrin-releasing peptide and vasoactive intestinal polypeptide are involved in the reception of the photic signal in the suprachiasmatic nucleus of the Syrian hamster: an immunocytochemical ultrastructural study

In mammals, the suprachiasmatic nuclei are involved in the generation of biological rhythms and are synchronized by light input coming from the retina. The targets of retinal afferents and the involvement of neurons containing gastrin-releasing and vasoactive intestinal peptides in photic reception were investigated in the suprachiasmatic nuclei of the Syrian hamster by using light- and electron-microscopic immunocytochemistry. Cholera toxin was used to trace retinal fibers and Fos immunoreactivity to visualize cellular response to light stimulation. Ultrastructural observations were made in the intermediate third of the nuclei, the area of highest overlap for the immunoreactivities investigated. Gastrin-releasing peptide and vasoactive intestinal peptide cell bodies were localized in the ventral part of the nuclei; their dense immunoreactive fiber network often displayed synaptic contacts. Both neuropeptides were colocalized in elongated cells observed near the optic chiasm. Following a light pulse in the middle of the subjective night, Fos protein was expressed in most gastrin-releasing peptide perikarya and in some vasoactive intestinal peptide cells. Retinal terminals mostly occurred in the midline zone between the suprachiasmatic nuclei. Symmetrical or asymmetrical retinal synapses were observed on gastrin-releasing peptide-immunoreactive dendrites and somata, but never on vasoactive intestinal peptide neurons. These results are discussed in relation to the photic entrainment of the circadian clock.     

Fatty acid remodeling in cellular glycerophospholipids following the activation of human T cells

Changes in fatty acid (FA) and glycerophospholipid (GPL) metabolism associated with cell cycle entry are not fully understood. In this study FA-GPL remodeling was investigated in resting and proliferating primary human T cells. Significant changes were measured in the composition and distribution of FAs in GPLs following receptor activation of human T cells. The FA distribution of proliferating T cells was very similar to that of the human Jurkat T cell line and when the stimulus was removed from proliferating T cells, they stopped proliferating and the FA distribution largely reverted back to that of resting T cells. The cellular content of saturated and monounsaturated FAs was significantly increased in proliferating cells, which was associated with an induction of FA synthase and stearoyl-CoA desaturase-1 gene expression. Additionally, cellular arachidonate was redistributed in GPLs in a distinct pattern that was unlike any other FAs. This redistribution was associated with an induction of CoA-dependent and CoA-independent remodeling. Accordingly, significant changes in the expression of several acyl-CoA synthetases, lysophospholipid acyltransferases, and phospholipase A₂ were measured. Overall, these results suggest that metabolic pathways are activated in proliferating T cells that may represent fundamental changes associated with human cell proliferation.