Effect of retinol dehydrogenase gene transfer in a novel rat model of Stargardt disease.

Dysfunction of the ATPase-binding Cassette Transporter protein (ABCA4) can lead to early onset macular degeneration, in particular to Stargardt disease. To enable translational research into this form of blindness, we evaluated the effect of Cas9-induced disruptions of the ABCA4 gene to potentially generate new transgenic rat models of the disease. We show that deletion of the short exon preceding the second nucleotide-binding domain is sufficient to drastically knock down protein levels and results in accumulation of retinoid dimers similar to that associated with Stargardt disease. Overexpression of the retinol dehydrogenase enzymes RDH8 and RDH12 can to a limited extent offset the increase in the bisretinoid levels in the Abca4Ex42-/ - KO rats possibly by restricting the time window in which retinal can dimerize before being reduced to retinol. However, in vivo imaging shows that overexpression of RDH8 can induce retinal degeneration. This may be due to the depletion in the outer segment of the cofactor NADPH, needed for RDH function. The translational potential of RDH therapy as well as other Stargardt disease therapies can be tested using the Abca4 knockdown rat model.

Roux-en-Y gastric bypass reduces plasma cholesterol in diet-induced obese mice by affecting trans-intestinal cholesterol excretion and intestinal cholesterol absorption.

OBJECTIVE: Bariatric surgery appears as the most efficient therapeutic alternative in morbidly obese patients. In addition to its efficiency to decrease body weight, it also improves metabolic complications associated to morbid obesity, including dyslipidemia. Although the cholesterol-lowering effect varies with the bariatric procedures, the underlying molecular mechanisms remain poorly defined. This study aims to assess the consequence of both restrictive (sleeve gastrectomy; SG) and malabsorptive (Roux-en-Y gastric bypass; RYGB) procedures on cholesterol metabolism in mice. SUBJECTS: Ten-week-old C57BL6/J males were fed with a high-fat diet for 8-14 weeks before sleeve or RYGB surgery. RESULTS: SG has a modest and transient effect on plasma cholesterol levels, linked to a reduction in food intake. In contrast, modified RYGB led to a sustained ≈35% reduction in plasma cholesterol concentrations with a drastic increase in fecal cholesterol output. Mechanistically, RYGB exerts a synergystic effect on cholesterol metabolism by inducing the trans-intestinal cholesterol efflux and reducing the intestinal cholesterol absorption. CONCLUSIONS: In mice, RYGB, but not sleeve, strongly favors plasma cholesterol elimination by concomitantly increasing trans-intestinal cholesterol excretion and by decreasing intestinal cholesterol absorption. Our models open new perspective for deciphering the hypocholesterolemic effects of bariatric procedures.

Fenofibrate decreases plasma ceramide in type 2 diabetes patients: A novel marker of CVD?

AIM: The benefit of the lipid-lowering drug fenofibrate on cardiovascular outcomes is controversial. Our aim was to find new circulating markers to identify those patients most likely to benefit from fenofibrate prescription. METHODS: Analyses were conducted of plasma samples collected from 102 patients with type 2 diabetes, enrolled in the FIELD trial, before and after fenofibrate treatment (200mg/day). Non-targeted and targeted lipid analyses and apolipoprotein measurements were made using mass spectrometry methods. RESULTS: Lipidomics revealed a global decrease in ceramide after fenofibrate treatment confirmed by quantitative analysis (-18.2%, P<0.001). These changes were strongly associated with those found for plasma sphingomyelin (r=0.80, P<0.001) and, to a lesser extent, for sphingosine-1-phosphate (r=0.34, P<0.001). Ceramide levels decreased in 73.5% of patients. In addition to the expected lipid changes (decreases in triglycerides, total cholesterol and LDL cholesterol, and increase in HDL cholesterol), fenofibrate also lowered plasma apoC-II (-11.1%, P<0.01), apoC-III (-24.6%; P<0.001), apoB100 (-27.0%, P<0.01) and sphingomyelinase (-7.6%, P<0.001), and increased plasma apoA-II (22.4%, P<0.001) as well as adiponectin (11.4%, P<0.001). No significant association was found between ceramide decrease and these modulations except for total cholesterol (r=0.20, P=0.047) and HDL protein components. At baseline, only elevated sphingolipid levels were significantly associated with ceramide reduction after fenofibrate treatment. CONCLUSION: Fenofibrate lowers plasma ceramide independently of the usual lipid parameters. As ceramide is a strong marker of atherosclerosis, our study underpins the need to further evaluate its contribution to cardiovascular events in fenofibrate-treated patients.