Skin cholesterol: test performance, evaluation of potential determinants and correlation analysis with cardiovascular risk factors and circulating markers of inflammation

The relationship between skin cholesterol testing and parameters of cardiovascular risk: a systematic review

BACKGROUND

A potential correlation between skin cholesterol levels obtained via skin biopsy and evidence of underlying atherosclerosis has been reported. With the availability of a noninvasive method of skin cholesterol measurement, multiple studies investigated the association of skin cholesterol and traditional cardiovascular risk factors. We provide a systematic review of clinical data to assist physicians counselling patients that have undergone skin cholesterol testing and to provide a framework for future research.

METHODS

Multiple electronic databases were systematically searched for studies published from 1970 through February 2013. Selection criteria included English language, peer-reviewed studies that quantitatively examined the relationship between noninvasively measured skin cholesterol levels and indices of vascular disease or cardiovascular risk factors in human subjects.

RESULTS

We identified 9 cohorts reported in 11 studies. The studies suggest that skin cholesterol does not correlate with traditional markers of cardiovascular disease such as serum lipid values and inflammatory markers, and integrated risk scores (Framingham and Prospective Cardiovascular Münster [PROCAM]). Single studies reported a significant relationship between skin cholesterol levels and evidence of underlying atherosclerosis as implied by positive exercise testing, invasive coronary angiography, increased calcium scores in Caucasian patients, and presence of carotid plaque detected using B-mode ultrasound. Two studies identified a significant relationship using B-mode measurements of carotid intima medial thickening.

CONCLUSIONS

Skin cholesterol might be a marker of underlying vascular atherosclerosis. Further prospective investigations are warranted to establish utility of this point-of-care test for identifying subjects warranting formal cardiovascular risk assessment.

The outer frontier: the importance of lipid metabolism in the skin

The skin serves the vital function of providing a barrier between the hostile external environment and the host. While the skin has many important barrier functions, the two that are absolutely essential for survival are the barrier to the movement of water and electrolytes (permeability barrier) and the barrier against invasive and toxic microorganisms (antimicrobial barrier). Lipids play an essential role in the formation and maintenance of both the permeability and antimicrobial barriers. A hydrophobic extracellular lipid matrix in the stratum corneum composed primarily of ceramides, cholesterol, and free fatty acids provides the barrier to the movement of water and electrolytes. A variety of lipids, such as fatty alcohols, monoglycerides, sphingolipids, phospholipids, and in particular free fatty acids, have antimicrobial activity and contribute to the antimicrobial barrier. In addition to these essential functions, we will also review the ability of skin surface cholesterol to reflect alterations in systemic lipid metabolism and the risk of atherosclerosis.

Skin tissue cholesterol is not related to vascular occlusive disease

The objective of the present study was to evaluate the role of skin tissue cholesterol (SkinTc) in predicting the presence of atherosclerosis. SkinTc concentrations were determined in 318 consecutive patients by using the non-invasive PREVU POC Skin Sterol Test. Additionally, a complete lipid status and cardiovascular risk profile according to the PROCAM and Framingham scores as well as an evaluation by carotid duplex sonography and ankle-brachial blood pressure index testing was obtained from all patients. SkinTc concentrations did not differ significantly among patients suffering from cerebrovascular disease (CVD) and peripheral arterial disease (PAD) compared to the corresponding control groups and among patients with a calculated cardiovascular risk > 10% in 10 years compared to patients with a risk < 10% (all p > 0.05). Additionally, SkinTc concentrations were not significantly higher in the 245 patients with at least one documented atherosclerotic disease compared with the remaining 73 patients without evidence of atherosclerosis. In conclusion, SkinTc concentrations determined by the PREVU POC Skin SterolTest are not related to the presence of CVD and PAD or to an elevated cardiovascular risk, indicating that this parameter cannot be used as a reliable indicator of atherosclerosis.