Design, synthesis, and biological evaluation of conformationally constrained glycerol 3-phosphate acyltransferase inhibitors

Abstract

Glycerol 3-phosphate acyltransferase (GPAT) isozymes are central control points for fat synthesis in mammals. Development of inhibitors of these membrane-bound enzymes could lead to an effective treatment for obesity, but is thwarted by an absence of direct structural information. Based on a highly successful study involving conformationally constrained glycerol 3-phosphate analogs functioning as potent glycerol 3-phosphate dehydrogenase inhibitors, several series of cyclic bisubstrate and transition state analogues were designed, synthesized, and tested as GPAT inhibitors. The weaker in vitro inhibitory activity of these compounds compared to a previously described benzoic acid series was then examined in docking experiments with the soluble squash chloroplast GPAT crystal structure. These in silico experiments indicate that cyclopentyl and cyclohexyl scaffolds prepared in this study may be occluded from the enzyme active site by two protein loops that sterically guard the phosphate binding region. In view of these findings, future GPAT inhibitor design will be driven toward compounds based on planar frameworks able to slide between these loops and enter the active site, resulting in improved inhibitory activity.

Pharmacological glycerol-3-phosphate acyltransferase inhibition decreases food intake and adiposity and increases insulin sensitivity in diet-induced obesity

“…However, if overinhibiting GPATs, or any one isoform, may carry serious health risk, it could be desirable instead to inhibit multiple GPATs at a more modest level. Nevertheless, work continues in the effort to design new GPAT inhibitors that target the catalytic domain more effectively (54), and such compounds may offer similar degree of biological effect as FSG67, but at lower concentration and dose ranges.…”

“…In practice, it might not yet be feasible to design compounds to target the specific isoforms, due to their similar catalytic domains. The crystal structure of GPAT from squash chloroplast was reported in 2001 (47) and has served as our template for designing GPAT inhibitors (53,54) because crystal structures for the mammalian isoforms are not yet available. In the current studies, our small-molecule GPAT inhibitor FSG67 likely inhibited multiple GPAT isoforms, although possibly to different extents.…”

“…The mitochondrial GPAT assay has been described (39). As we have done previously (53)(54), isolated mitochondria were added to an incubation mixture with [ 14 C]glycerol-3-phosphate, palmitoyl-CoA, and varying concentrations of FSG67. For the current determinations, the assay was run with or without the sulfhydryl-reactive compound NEM (100 M) to distinguish the NEM-insensitive GPAT1 activity from that of NEM-inactivated GPAT2 (29).…”

Chemical modulation of glycerolipid signaling and metabolic pathways

“…A second class of GPAT inhibitors attempted to mimic the structure of fatty acyl-CoAs with alkylsulfonamide and carboxylate groups. Unfortunately, these compounds did not significantly inhibit GPAT catalytic activity [305]. …”

Aralia cordata Inhibits Triacylglycerol Biosynthesis in HepG2 Cells

“…Recently, a couple of GPAT inhibitors have been reported. 20,21 However, the pharmacological validation of their use in cells and animal models remains to be examined.…”