Cancer Letters, 65 (1992) 169- 171

Elsevier Scientific Publishers Ireland Ltd.

Tissue lipid composition of human gliomas and meningiomas

Emine KBkoglu”, Altan G6rsevala, Hiiseyin S6nmeza and Emin ozyurtb

Department of ‘Biochemistry and bNeurosurgey, Cerrohpaga Medical Faculty, Istanbul (Turkey)

(Received 13 August 1991) (Accepted 2 June 1992)

summr9

This study is a comparative analysis of some lipid fractions in human brain tumors and nor- mal brain tissue. Gliomas and meningiomas were studied and in these tumors while total lipid, total and free cholesterol and total phosphoglyceride levels were found to be significantly lower than in normal controls, the difference in esterified cholesterol levels was found to be insignificant. No significant dif- ferences in lipid fractions existed between gliomas and meningiomas except total and esterified cholesterol values.

Kvord~: human gliomas; human men- ingioma; lipid; cholesterol; phosphoglyceride

IntrodWti0n

Various studies have been performed aim- ing to demonstrate the existence of a correla- tion between body lipid composition and cancer types. Most of these researches have focused on the relation between serum cholesterol levels and the incidence of colon cancer. However, a wide range of variation was observed in the results, some implying an inverse relation between serum cholesterol levels and the incidence of colon cancer [5 - 7,9] whereas several others proposed that

Correspondence to: Emine Kiiko&, Department of

Biochemistry, Cerrahpasa Medical Faculty, Istanbul, Turkey.

169

no correlation existed between these two parameters [lo]. Investigations were also per- formed to establish a connection between serum cholesterol and the incidence of lung, pancreas and stomach cancers [7, lo]. Despite the numerous comparative studies which aimed to reach a correlation between the in- cidence and lipid patterns of cancers, the number of studies concerning the differences between the lipid composition of normal tissues and those of the tumors seems to be scarce. For that reason we compared the total lipid, total, esterified and free cholesterol and phosphoiipid levels of meningiomas and gliomas with those of normal brain tissues.

Materiala and Methods

Tumoral tissue samples were obtained from the Neurosurgery Department immediately after surgical intervention. No chemotherapy known to affect the lipid metabolism was used in the treatment of the disease. Macroscopical- ly homogenous pieces of tumor were selected and samples were sent to the Department of Pathology for identification. Normal brain tissues were obtained at autopsy within a max- imum of 5 h following death. All the samples were put into physiological saline and frozen at - ZOOC.

Extraction of lipids Lipids were extracted from tissues employ-

ing the procedure of Folch et al. [3] Tissue

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samples were homogenized in a mixture of chloroform/methanol (2/l, v/v), the ratio of tissue weight to the solvent mixture being ad- justed to 1 g/10 ml. After filtration the extracts were kept at 4OC.

Results and Diacassion

Total lipid determination in homogenates was performed by the phosphovanilin method [4]. The results were given in mg/ 100 mg wet tissue.

The findings for all lipid fractions are presented in Table I. The content of all lipid fractions of the tumors was lower than in nor- mal brain tissue. While highly significant dif- ferences (P < 0.001) were observed to exist between total lipid, total cholesterol, total phosphoglyceride and free cholesterol levels of tumor tissue and those of control group, the difference between esterified cholesterol levels was found to be insignificant (P > 0.05).

Determination of total phosphoglyceride levels In each homogenate, total phosphoglyce-

ride levels were assayed using the procedure of Zilversmit et al. [12]. The results were given in mg/lOO mg wet tissue.

Determination of total cholesterol After the homogenates had been desiccated

on a hot water bath, the precipitates were dissolved in propranol and from these solu- tions total cholesterol determinations were per- formed [l]. The results were given in mg per 100 mg wet tissue.

Determination of free and estherified cholesterol levels

The deviations in lipid content of men- ingiomas and of gliomas are presented in Table II. The content of all lipid fractions are significantly lower in meningiomas than in nor- mal- tissues (P < 0.001). In gliomas it was observed that the differences between total lipid, total phosphoglyceride and cholesterol levels of tumor tissues and those of control group were highly significant (P < 0.001). However, the differences between esterified and free cholesterol levels of gliomas and those of control group were unsignificant (P > 0.05). Table II also indicates that no significant differences in lipid fractions existed between giiomas and meningiomas except total and esterified cholesterol values (P < 0.05).

In the solutions prepared with propranol, A recent study about the content of lipid free cholesterol was precipitated by adding 1% fractions in brain was performed by Yates et al. digitonin. On the upper phase of the solution [ll] whose results were similar to ours in- esterified cholesterol was determined by en- dicating that the content of all lipid fractions of zymatic method [l]. By subtracting the the brain tumors were significantly different esterified cholesterol values from total from those of normal brain tissues. However, cholesterol values we obtained free cholesterol Das and Isichei [2] showed a marked rise in all levels. The results were given in mg/lOO mg lipid fractions, especially in cholesterol levels, wet tissue. in thyroid tissues of the patients with thyroid

Table I. Lipid content of human tumoral brain tissue and normal brain tissue.

Type N Total Total Estherified Free

lipid cholesterol cholesterol cholesterol

Tumor 17 2.76”* 0.52”zt 0.45b f 0.19”*

tissues 1.04 0.33 0.35 0.09

4.77* l.OO* 0.62 + 0.37 f

Normals 9 0.63 0.16 0.11 0.12

In comparison with normal tissues. "P < 0.001. bP > 0.05.

Total phospho- glyceride

0.50” f 0.16 1.16~ 0.28

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Table II. Lipid content of gliomas, meningiomas and normal brain tissues.

Type N Total Total Estherified Free Total

lipid cholesterol cholesterol cholesterol phosphoglyceride

2.69” * 0.70b* 0.62’zt 0.23’~ 0.44” l Glioma 9 0.70 0.36 0.40 0.21 0.15

2.52”zt 0.32”* 0.23” zt 0.13”+ 0.59” f Meningioma8 1.34 0.13 0.039 0.04 0.18

4.77* l.OO* 0.62* 0.37 f 1.16~ Normals 9 0.63 0.16 0.11 0.12 0.28

In comparison with normal tissues. “P < 0.001. bP c 0.05. ‘P > 0.05.

tumors. This observation is contrary to our findings.

Cholesterol is an important structural unit of bilayer cell membrane [8]. Also it is recognized that cholesterol is a major lipid component of the brain [ES]. The lower cholesterol content of meningiomas and of gliomas might be due to the enhanced rate of membrane synthesis associated with cell proliferation. Besides malignant transformation might be presumed to be responsible for the modifications induced in cellular lipid metabolism. The differences in all lipid fractions between tumor tissues and normal tissues may be explained by the idea that complex biochemical alterations occurring at the membrane level during the neoplastic process affects the lipid metabolism of the cell. However, the degree and the type of altera- tions induced probably depends on the histogenetic type of the tumor and its degree of differentiation. As cellular activity of malignant growth is quiet different from that of normal tissue, its biochemical structure is also ex- pected to be diverging from normal pro- portions.

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