N,N-Dimethyl-3β-hydroxycholenamide Reduces Retinal Cholesterol via Partial Inhibition of Retinal Cholesterol Biosynthesis Rather Than its Liver X Receptor Transcriptional Activity

Abstract

N,N-dimethyl-3β-hydroxycholenamide (DMHCA) is an experimental pharmaceutical and a steroidal liver X receptor (LXR) agonist, which does not induce undesired hepatic lipogenesis. Herein, DMHCA was evaluated for its retinal effects on normal C57BL/6J and Cyp27a1−/−Cyp46a1−/− mice; the latter having higher retinal total and esterified cholesterol in addition to retinal vascular abnormalities. Different doses and two formulations were used for DMHCA delivery either via drinking water (C57BL/6J mice) or by oral gavage (Cyp27a1−/−Cyp46a1−/− mice). The duration of treatment was 1 week for C57BL/6J mice and 2 or 4 weeks for Cyp27a1−/−Cyp46a1−/− mice. In both genotypes, the higher DMHCA doses (37–80 mg/kg of body weight/day) neither increased serum triglycerides nor serum cholesterol but altered the levels of retinal sterols. Total retinal cholesterol was decreased in the DMHCA-treated mice, mainly due to a decrease in retinal unesterified cholesterol. In addition, retinal levels of cholesterol precursors lanosterol, zymosterol, desmosterol, and lathosterol were changed in Cyp27a1−/−Cyp46a1−/− mice. In both genotypes, DMHCA effect on retinal expression of the LXR target genes was only moderate and gender-specific. Collectively, the data obtained provide evidence for a decrease in retinal cholesterol as a result of DMHCA acting in the retina as an enzyme inhibitor of cholesterol biosynthesis rather than a LXR transcriptional activator. Specifically, DMHCA appears to partially inhibit the cholesterol biosynthetic enzyme Δ24-dehydrocholesterol reductase rather than upregulate the expression of LXR target genes involved in reverse cholesterol transport. The identified DMHCA dosages, formulations, and routes of delivery as well as the observed effects on the retina should be considered in future studies using DMHCA as a potential therapeutic for age-related macular degeneration and diabetic retinopathy.

Retinal Cholesterol Content Is Reduced in Simvastatin-Treated Mice Due to Inhibited Local Biosynthesis Albeit Increased Uptake of Serum Cholesterol

“…All animal experiments were in compliance with the Guide for Care and Use of Laboratory Animals by the National Institutes of Health and were approved by Case Western Reserve University's Animal Care and Use Committee. Female and male mice have similar levels of serum and retinal sterols and show the same pattern of sterol changes in response to drug treatment (El-Darzi et al, 2018). Yet, female mice typically have higher data variability due to monthly hormonal fluctuations.…”

Selective LXR agonist DMHCA corrects retinal and bone marrow dysfunction in type 2 diabetes

“…N, N-dimethyl-3β-hydroxy-cholenamide (DMHCA) is a synthetic oxysterol that induces gene-specific modulation of LXR (22)(23)(24). Mechanistically, DMHCA activates LXR through direct agonism, as well as the inhibition of desmosterol reduction, the final step in the predominant cholesterol biosynthesis pathway, leading to the accumulation of the potent LXR agonist desmosterol (25,26). During endogenous LXR activation, compensatory fatty acid biosynthesis is stimulated through the transcriptional induction of SREBP1c, leading to elevated triglyceride levels (26).…”

“…Mechanistically, DMHCA activates LXR through direct agonism, as well as the inhibition of desmosterol reduction, the final step in the predominant cholesterol biosynthesis pathway, leading to the accumulation of the potent LXR agonist desmosterol (25,26). During endogenous LXR activation, compensatory fatty acid biosynthesis is stimulated through the transcriptional induction of SREBP1c, leading to elevated triglyceride levels (26). Intriguingly, DMHCA selectively activates the cholesterol efflux arm of the LXR pathway, through the induction of ATP-binding cassette transporter (ABCA1), with minimal effect on SREBP1c compared with other LXR agonists, such as T0901317 and GW3965 (25)(26)(27)(28)(29).…”

“…During endogenous LXR activation, compensatory fatty acid biosynthesis is stimulated through the transcriptional induction of SREBP1c, leading to elevated triglyceride levels (26). Intriguingly, DMHCA selectively activates the cholesterol efflux arm of the LXR pathway, through the induction of ATP-binding cassette transporter (ABCA1), with minimal effect on SREBP1c compared with other LXR agonists, such as T0901317 and GW3965 (25)(26)(27)(28)(29). Thus, DMHCA has lower risk for the undesirable adverse effects that plagued previous LXR modulators, while retaining the ability to lower circulating LDL and restore peripheral cholesterol homeostasis (22,28).…”

Liver X Receptor Activation with an Intranasal Polymer Therapeutic Prevents Cognitive Decline without Altering Lipid Levels

“…In previously reported studies of DMHCA, experimental doses in mice ranged from 8 to 80 mg/kg body weight/day for systemic or oral administration, without penetration through the BBB. ,, We explored a range of four different doses of DMHCA, 0.3, 1.5, 3, and 15 mg/kg body weight/day, equivalent to 1.5, 7.5, 15, and 75 mg of PEG-[G1]-DMHCA/kg body weight/day. Animals were divided in five groups ( n = 4 per group) and received a single intranasal dose with increasing concentrations of DMHCA micelles (10 μL total volume, 5 μL/nostril).…”