2 research outputs found
Use of [<sup>13</sup>C<sub>18</sub>] Oleic Acid and Mass Isotopomer Distribution Analysis to Study Synthesis of Plasma Triglycerides In Vivo: Analytical and Experimental Considerations
We have previously reported on a
liquid chromatography–mass
spectrometry method to determine the disposition of [<sup>13</sup>C<sub>18</sub>]-oleic acid following intravenous and oral administration
in vivo. This approach has enabled us to study a variety of aspects
of lipid metabolism including a quantitative assessment of triglyceride
synthesis. Here we present a more rigorous evaluation of the constraints
imposed upon the analytical method in order to generate accurate data
using this stable-isotope tracer approach along with more detail on
relevant analytical figures of merit including limits of quantitation,
precision, and accuracy. The use of mass isotopomer distribution analysis
(MIDA) to quantify plasma triglyceride synthesis is specifically highlighted,
and a re-evaluation of the underlying mathematics has enabled us to
present a simplified series of equations. The derivation of this MIDA
model and the significance of all underlying assumptions are explored
in detail, and examples are given of how it can successfully be applied
to detect differences in plasma triglyceride synthesis in lean and
high-fat diet fed mouse models. More work is necessary to evaluate
the applicability of this approach to triglyceride stores with slower
rates of turnover such as in adipose or muscle tissue; however, the
present report provides investigators with the tools necessary to
conduct such studies
Development of Anti-CD74 Antibody–Drug Conjugates to Target Glucocorticoids to Immune Cells
Glucocorticoids (GCs)
are excellent anti-inflammatory drugs but
are dose-limited by on-target toxicity. We sought to solve this problem
by delivering GCs to immune cells with antibody–drug conjugates
(ADCs) using antibodies containing site-specific incorporation of
a non-natural amino acid, novel linker chemistry for in vitro and
in vivo stability, and existing and novel glucocorticoid receptor
(GR) agonists as payloads. We directed fluticasone propionate to human
antigen-presenting immune cells to afford GR activation that was dependent
on the targeted antigen. However, mechanism of action studies pointed
to accumulation of free payload in the tissue culture supernatant
as the dominant driver of activity and indeed administration of the
ADC to human CD74 transgenic mice failed to activate GR target genes
in splenic B cells. Suspecting dissipation of released payload, we
designed an ADC bearing a novel GR agonist payload with reduced permeability
which afforded cell-intrinsic activity in human B cells. Our work
shows that antibody-targeting offers significant potential for rescuing
existing and new dose-limited drugs outside the field of oncology