Pharmacological chaperone action in humanized mouse models of MC4R-linked obesity.

Preclinical animal study using humanized mouse models to test pharmacological chaperones for MC4R-linked obesity

“The present study aimed at determining whether pharmacological chaperones (PCs) that restore folding and plasma membrane trafficking by stabilizing near native protein conformation may represent valid therapeutic avenues for the treatment of melanocortin type 4 receptor–linked (MC4R-linked) obesity.”

Humanized MC4R knockin mice expressing either wild-type or R165W mutant human MC4R, and loxTB MC4R-null mice

“To test the therapeutic PC potential, we engineered humanized MC4R (hMC4R) mouse models expressing either the WT human MC4R or a prevalent obesity-causing mutant (R165W).”

More than 4 mice per group in in vivo experiments

“We chose a randomized crossover experimental design with a 2-day washout period in order to reduce number of animals used in each experiment, with n > 4 mice per group to achieve statistical significance.”

Phenotyping and treatment assessments conducted over several weeks, including chronic infusion studies lasting 14 days

“The pumps, which deliver their content at a flow rate of 0.25 μL/h for 14 days, were subcutaneously implanted in the interscapular region.”

Pharmacological chaperone UM0130866 restored the anorexigenic response to melanocortin agonist in mice with the R165W mutation

“Administration of a PC able to rescue cell surface expression and functional activity of R165W-hMC4R in cells restored the anorexigenic response of the R165W-hMC4R obese mice to melanocortin agonist, providing a proof of principle for the therapeutic potential of MC4R-targeting PCs in vivo.”

Wild-type human MC4R mice exhibited lower sensitivity to α-MSH compared to mouse MC4R, leading to a hypomorphic obese phenotype

“Interestingly, the expression of the WT-hMC4R in mice revealed lower sensitivity of the human receptor to α–melanocyte-stimulating hormone (α-MSH) but not β-MSH or melanotan II, resulting in a lower penetrance obese phenotype in the WT-hMC4R versus R165W-hMC4R mice.”

R165W-hMC4R mice displayed impaired glucose tolerance and insulin resistance

“As shown in Figure 5B, an impaired response to insulin injection was observed in both male and female homozygous R165W-hMC4R mice measured at 17–18 and 27–28 weeks, indicative of insulin resistance.”

The impact of chronic pharmacological chaperone treatment on weight loss has not yet been investigated

“The present study clearly demonstrated that PC treatment could restore the anorexic response of homozygous R165W-hMC4R mice to acute treatment with melanocortin receptor agonist. However, the impact of chronic PC treatment on weight loss remains to be investigated.”