Does APOE genotype modify the relations between serum lipid and erythrocyte omega-3 fatty acid levels?

Incidental finding of lipaemia retinalis on diabetic retinal screening

SUMMARY

A 37-year-old female of South Asian origin was referred to our diabetes clinic for evaluation of an unusual finding during her retinal screening. Her retinal blood vessels appeared white in contrast to the normal pink-red colour. She had type I hyperlipidaemia, confirmed by genotype, and was recently diagnosed with diabetes, secondary to pancreatic insufficiency, for which she had suboptimal control and multiple hospitalisations with recurrent pancreatitis. On examination, she had multiple naevi on her skin; the rest of the examination was unremarkable. The patient did not report any visual disturbances and had intact visual acuity. Investigations showed raised total cholesterol (12.5 mmol/L) and triglycerides (57.7 mmol/L). Following evaluation, the patient was diagnosed with lipaemia retinalis, secondary to type I hyperlipidaemia. The patient was managed conservatively to reduce the cholesterol and triglyceride burdens. However, therapies with orlistat, statin, fibrates and cholestyramine failed. Only a prudent diet, omega-3 fish oil, medium-chain triglycerides oil and glycaemic control optimised with insulin showed some improvements in her lipid profile. Unfortunately, this led her to becoming fat-soluble vitamin deficient; hence, she was treated with appropriate supplementation. She was also recently started on treatment with volanesorsen. Following this, her lipid parameters improved and lipaemia retinalis resolved.

LEARNING POINTS

Lipaemia retinalis is an uncommon incidental finding of type I hyperlipidaemia that may not affect vision. Management of associated dyslipidaemia is challenging with minimal response to conventional treatment. Increased awareness of lipaemia retinalis and specialist management is needed as part of regular patient monitoring and personalised management.

Impact of Genotype on EPA and DHA Status and Responsiveness to Increased Intakes

At a population level, cardioprotective and cognitive actions of the fish oil (FO) derived long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been extensively demonstrated. In addition to dietary intake, which is limited for many individuals, EPA and DHA status is dependent on the efficiency of their biosynthesis from α-linolenic acid. Gender and common gene variants have been identified as influencing the rate-limiting desaturase and elongase enzymes. Response to a particular intake or status is also highly heterogeneous and likely influenced by genetic variants which impact on EPA and DHA metabolism and tissue partitioning, transcription factor activity, or physiological end-point regulation. Here, available literature relating genotype to tissue LC n-3 PUFA status and response to FO intervention is considered. It is concluded that the available evidence is relatively limited, with much of the variability unexplained, though APOE and FADS genotypes are emerging as being important. Although genotype × LC n-3 PUFA interactions have been described for a number of phenotypes, few have been confirmed in independent studies. A more comprehensive understanding of the genetic, physiological and behavioural modulators of EPA and DHA status and response to intervention is needed to allow refinement of current dietary LC n-3 PUFA recommendations and stratification of advice to “vulnerable” and responsive subgroups.