Jing Ma, MD, PhD Associate Professor of Medicine
Harvard Medical School
Associate Epidemiologist, Department of Medicine
I have an ongoing interest in biochemical/molecular markers and risk of cardiovascular disease (CVD) and colorectal cancer. My current research involves: 1) Biochemical markers of dietary intake (e.g. iron, folate, vitamin D, selenium, and fatty acids); 2) biological markers (e.g. insulin-like growth factor I [IGF-I], C-reactive protein, fibrinogen, and lipids); 3) molecular markers (polymorphisms of MTHFR, MTR, vitamin D receptor, and HFE) and gene-environment interactions. Using a nested case-control study design, I found that a polymorphism of methylenetetrahydrofolate (MTHFR), a key enzyme in folate metabolism, was associated with lower plasma folate and higher homocysteine levels. Men homozygous for the polymorphism had a decreased risk of colorectal cancer. I found no apparent association between this polymorphism and risk of myocardial infarction. I have been involved in a study which found that men with elevated plasma levels of IGF-I had significantly increased risk of prostate cancer. I am also involved in studies of lipids and fatty acids -- atherogenic markers, fibrinogen -- a thrombotic marker, and C-reactive protein -- a marker of inflammation, in association with risk of CVD.
The iron-CVD/cancer hypotheses have been supported by laboratory and animal studies showing that iron increases production of free oxygen radicals leading to lipid preoxidation of cell membranes, subsequent call damage and DNA breaks. However, findings from small epidemiologic studies are inconsistent. I am currently studying the relation between iron status (intake, body stores, and genetic susceptibility for hemochromatosis, HFE) and risk of CVD and colorectal cancer. I plan to evaluate the individual associations of intake, biomarker levels, and HFE genotype with risk of CVD and colorectal cancer, as well as the gene-environment interactions. Further, I will evaluate gender, dietary and lifestyle factors that may account for or modify the association between iron and risk of CVD and colorectal cancer.
Ma J, Folsom AR, Melnick SL, Eckfeldt JH, Sharrett AR, Nabulsi AA, Hutchinson RG, Metcalf PA. Associations of serum and dietary magnesium with cardiovascular disease, hypertension, diabetes, insulin, and carotid arterial wall thickness: the ARIC study. Atherosclerosis Risk in Communities Study. J Clin Epidemiol. 1995 Jul;48(7):927-40. [abstract]
Ma J, Folsom AR, Shahar E, Eckfeldt JH. Plasma fatty acid composition as an indicator of habitual dietary fat intake in middle-aged adults. The Atherosclerosis Risk in Communities (ARIC) Study Investigators. Am J Clin Nutr. 1995 Sep;62(3):564-71. [abstract]
Ma J, Folsom AR, Eckfeldt JH, Lewis L, Chambless LE. Short-term and long-term repeatability of fatty acid composition of human phospholipids and cholesterol eaters. Am J Clin Nutr. 1995 Sep;62(3):572-8. [abstract]
Ma J, Stampfer MJ, Hennekens CH, Frosst P, Selhub J, Horsford J, Malinow MR, Willett WC, Rozen R. Methylenetetrahydrofolate reductase polymorphism, plasma folate, homocyst(e)ine, and risk of myocardial infarction in US physicians. Circulation. 1996 Nov 15;94(10):2410-6. [abstract]
Stampfer MJ, Krauss RM, Ma J, Blanche PJ, Moll LG, Sacks FM, Hennekens CH. A prospective study of triglyceride level, low-density lipoprotein particle diameter, and risk of myocardial infarction. JAMA. 1996 Sep 18;276(11):882-8. [abstract]
Gann P, Ma J, Hennekens CH, Hollis BW, Haddad JG, Stampfer MJ. Circulating vitamin D metabolites in relation to subsequent development of prostate cancer. Cancer Epidemiol Biomarkers Prev. 1996 Feb;5(2):121-6. [abstract]
Ma J, Stampfer MJ, Giovannucci E, Artigas C, Hunter DJ, Fuchs C, Willett WC, Selhub J, Hennekens CH, Rozen R. Methylenetetrahydrofolate reductase polymorphism, dietary interactions, and risk of colorectal cancer. Cancer Res. 1997 Mar 15;57(6):1098-102. [abstract]
Ma J, Folsom AR, Lewis L, Eckfeldt JH. Relation of plasma phospholipid and cholesterol ester fatty acid composition to carotid artery intima-media thickness: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Clin Nutr. 1997 Feb;65(2):551-9. [abstract]
Ma J, Stampfer MJ, Christensen B, Giovannucci E, Hunter DJ, Willett WC, Selhub J, Hennekens CH, Gravel R, Rozen R. A polymorphism of methionine synthase gene: a link to risk of colorectal cancer? (Abstract) Am J Epidemiol 1998;147:s65.
Ma J, Stampfer MJ, Gann PH, Hough HL, Giovannucci E, Kelsey KT, Hennekens CH, Hunter DJ. Vitamin D receptor polymorphisms, circulating vitamin D metabolites, and risk of prostate cancer in United States physicians. Cancer Epidemiol Biomarkers Prev. 1998 May;7(5):385-90. [abstract]
Chan JM, Stampfer MJ, Giovannucci E, Gann PH, Ma J, Wilkinson P, Hennekens CH, Pollak M. Plasma insulin-like growth factor-I and prostate cancer risk: a prospective study. Science. 1998 Jan 23;279(5350):563-6. [abstract]
Zheng Z, Folsom AR, Ma J, Arnett DK, McGovern PG, Eckfeldt JH. Plasma fatty acid composition and 6-year incidence of hypertension in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Epidemiol. Am J Epidemiol. 1999 Sep 1;150(5):492-500. [abstract]