Proton magnetic resonance spectroscopy and single photon emission computed tomography study of the brain in asymptomatic young hyperlipidaemic Asian Indians in North India show early abnormalities

Abstract

Objective: To evaluate brain metabolism and cerebral blood flow in young patients with hyperlipidaemia. Patients and Methods: Proton magnetic resonance spectroscopy (¹H MRS) and single photon emission computed tomography (SPECT) of the brain was carried out in 19 asymptomatic young patients with hyperlipidaemia (mean age 32.6 ± 6.0 years, range 22-45 years) and 21 age-matched healthy controls divided into the following three groups; (i) hyperlipidaemics on pharmacological treatment (group 1, n = 13), (ii) hyperlipidaemics not on pharmacological treatment (group 2, n = 6) and (iii) control group of healthy subjects (group 3, n = 21). Results: No statistical difference was observed in the brain metabolite ratios between controls and hyperlipidaemic patients (both treatment naive and treated) in the ¹H NMR study. Two hyperlipidaemic patients showed a lactate peak and one had a lipid peak. The SPECT study was abnormal in seven hyperlipidaemic patients. In the pooled data, 50% subjects with high serum triglyceride (TG) levels as opposed to 14% subjects with normal serum TG levels showed cerebral hypoperfusion. The choline/creatine (Cho/Cr) ratio of the occipital region of the brain showed correlation with the excess percentage of body fat (%BF) and low levels of high density lipoprotein cholesterol (HDL-C) compared to those with normal %BF and normal HDL-C levels, respectively, in pooled data of all subjects. The N-acetyl aspartate (NAA)/Cho ratio also showed correlation with hypercholesterolaemia. Serum TG levels were positively correlated with the NAA/Cr ratio (r = 0.62, P < 0.05) and the Cho/Cr ratio (r = 0.63, P < 0.05) in the parieto-temporal area in group 1 patients. Conclusion: The study revealed no difference in the brain metabolite ratios between controls and hyperlipidaemic patients, while some hyperlipidaemic patients showed abnormalities of cerebral blood flow. Brain metabolite ratios were also influenced by certain parameters of body composition and lipids. As abnormal body composition, hypertriglyceridaemia and low levels of HDL-C are prevalent in Asian Indians, such data are important and indicate a need for further study.