Role of de novo lipogenesis in inflammation and insulin resistance in Alzheimer's disease.

Patients with Alzheimer's disease (AD) display both peripheral tissue and brain insulin resistance, the later could be a potential risk factor for cognitive dysfunction. While certain degree of inflammation is required for inducing insulin resistance, underlying mechanism(s) remains unclear. Evidence from diverse research domains suggest that elevated intracellular fatty acids of de novo pathway can induce insulin resistance even without triggering inflammation; however, the effect of saturated fatty acids (SFAs) could be detrimental due the development of proinflammatory cues. In this context, evidence suggest that while lipid/fatty acid accumulation is a characteristic feature of brain pathology in AD, dysregulated de novo lipogenesis could be a potential source for lipid/fatty acid accumulation. Therefore, therapies aimed at regulating de novo lipogenesis could be effective in improving insulin sensitivity and cognitive function in patients with AD.

Gender Differences Associated with Hyper-Inflammatory Conditions in COVID-19 Patients.

COVID-19 has been associated with various hyper-inflammatory conditions (HICs) such as macrophage activation, hematological dysfunction, cytokinaemia, coagulopathy, and liver inflammation. However, it is not clear if the differences in the disease severity and mortality shown by male and female COVID-19 patients are associated with these HICs. Here, we review the literature and present supporting laboratory data on the gender differences associated with various HICs in COVID-19 patients. We measured plasma/serum levels of various HIC specific clinical markers in severe male (N=132) and severe female (N=78) COVID-19 patients. The result revealed that all clinical markers were highly elevated above the normal in both male and female COVID-19 patients. However, a comparison of AUROC (area under the receiving operative characteristics) of specific clinical markers revealed that elevation in serum ferritin (marker for macrophage activation), and neutrophil to lymphocyte (N/L) ration (marker for hematological dysfunction) was much higher in male compared to the female COVD-19 patients. Further, univariate regression analyses revealed that male COVID-19 patients had two times higher risks than female patients for developing macrophage activation (OR 2.36, P=0.004)), hematological dysfunctions (OR 2.23, P=0.01), coagulopathy (OR 2.10, P=0.01), and cytokinaemia (OR 2.31, P=0.01). Similar results were obtained in bivariate analyses. Survival curve analysis showed that male COVID-19 patients had relatively short survival duration than female COVID-19 patients (hazard ratio 2.0, 95% CI 1.3-3.7, P=0.01). The above findings suggest that the high mortality rate in male COVID-19 patients compared to the female could be due to higher prevalence and severity of various HICs.

Cloning and functional characterization of the smooth muscle ether-a-go-go-related gene K+ channel. Potential role of a conserved amino acid substitution in the S4 region.

The human ether-a-go-go-related gene (HERG) product forms the pore-forming subunit of the delayed rectifier K(+) channel in the heart. Unlike the cardiac isoform, the erg K(+) channels in native smooth muscle demonstrate gating properties consistent with a role in maintaining resting potential. We have cloned the smooth muscle isoform of HERG, denoted as erg1-sm, from human and rabbit colon. erg1-sm is truncated by 101 amino acids in the C terminus due to a single nucleotide deletion in the 14th exon. Sequence alignment against HERG showed a substitution of alanine for valine in the S4 domain. When expressed in Xenopus oocytes, erg1-sm currents had much faster activation and deactivation kinetics compared with HERG. Step depolarization positive to -20 mV consistently produced a transient outward component. The threshold for activation of erg1-sm was -60 mV and steady-state conductance was approximately 10-fold greater than HERG near the resting potential of smooth muscle. Site-directed mutagenesis of alanine to valine in the S4 region of erg1-sm converted many of the properties to that of the cardiac HERG, including shifts in the voltage dependence of activation and slowing of deactivation. These studies define the functional role of a novel isoform of the ether-a-go-go-related gene K(+) channel in smooth muscle.

Fenamate-induced enhancement of heterologously expressed HERG currents in Xenopus oocytes.

The human ether-a-go-go related gene (HERG) product encodes for the pore-forming subunit of the rapid component of the delayed rectifier K(+) channel that mediates repolarization of cardiac action potential. HERG channels are also potential targets of a large variety of pharmacological agents most of which tend to block HERG currents. In this study, we examined the effects of the non-steroidal anti-inflammatory agents, flufenamic acid and niflumic acid, on heterologously expressed HERG channels in oocytes. The cRNA of HERG (30 ng) was injected into Xenopus oocytes and currents were recorded using two-electrode voltage clamp technique in a low Cl(-) solution. Flufenamic and niflumic acids (10(-4)-5 x 10 (-4) M) enhanced the amplitude of outward currents evoked by depolarizing pulses. At potentials positive to 0 mV, an initial transient component was also evident in the presence of fenamates. Fenamates accelerated the activation rate of HERG channels and decelerated their deactivation. Flufenamic acid (5 x 10 (-4) M) shifted the I(tail)-V relationship from -26.7+/-0.1 to -31.4+/-0.2 mV. Neither flufenamic acid or niflumic acid affected the kinetics of HERG channel inactivation. Using a voltage protocol that mimicked the cardiac action potential, both fenamates increased the outward current during the plateau and during the phase 3 repolarization of action potential. The effects of the fenamates were blocked by the HERG channel blocker, E-4031 and were also not observed in water-injected oocytes. Our data suggest that fenamates enhance HERG currents and affect the action potential duration in the heart.

Coupling of M2 muscarinic receptor to L-type Ca channel via c-src kinase in rabbit colonic circular smooth muscle.

BACKGROUND & AIMS: The L-type Ca(2+) channel is a major pathway for Ca(2+) influx in colonic smooth muscle and is modulated by endogenous levels of nonreceptor tyrosine kinase, c-src. Tyrosine kinases are also activated by G-protein-coupled receptors (GPCR). This study determined whether muscarinic receptor couples to Ca(2+) channels via c-src kinase. METHODS: Currents were measured in rabbit colonic smooth muscle cells and in transfected HEK293 cells by patch-clamp technique. Tyrosyl phosphorylated proteins were detected by Western blots and the interaction of c-src with the c-terminus of alpha subunit of Ca(2+) channel was determined by a GST pull-down assay. RESULTS: Methacholine (10 micromol/L) enhanced Ca(2+) channel currents by 30% under conditions whereby the M(3) receptor pathway was blocked by either 4-DAMP or by intracellular dialysis with anti-Galphaq antibody. Similar effects were observed by blocking intracellular Ca(2+) release with heparin. Enhancement was abolished by intracellular anti-Galphai antibody and by the c-src inhibitor, PP2 but unaffected by the inactive analog PP3. Immunoblot with anti-src antibody revealed increased src phosphorylation by muscarinic receptor stimulation. Purified c-src directly associated with the c-terminus of alpha1c subunit of the Ca(2+) channel. In M(2) receptor transfected HEK293 cells, currents were enhanced 2-fold by carbachol. CONCLUSIONS: These studies demonstrate stimulation of Ca(2+) current in colonic smooth muscle cells by M2 receptor coupled to Galphai-G protein and c-src activation. They also suggest a central role of c-src kinase in the cross-talk between tyrosine kinase receptor and GPCR.