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Normal triglyceride levels despite insulin resistance in African Americans: role of lipoprotein lipase.
Metabolism. 2005 Jul; 54(7):902-9.M

Abstract

Abstract Lipoprotein lipase (LPL), the enzyme responsible for hydrolyzing triglyceride (TG) in plasma lipoproteins, is a key regulator of plasma TG levels. In Caucasians, postheparin-LPL (PH-LPL) activity is impaired in the presence of insulin resistance and leads to elevated TG levels. However, African Americans are often both insulin-resistant and normotriglyceridemic. But in African Americans, the effect of insulin resistance on PH-LPL activity has not been studied. In African Americans, if insulin resistance is not associated with a decrease in PH-LPL activity, this could account for the simultaneous presence of insulin resistance and normotriglyceridemia. Therefore, our goal was to determine in African Americans the relationship between insulin resistance and PH-LPL activity. In a cross-sectional study of 107 nondiabetic African Americans (57 men and 50 women; age mean +/- SD, 35 +/- 8 years, range 22-50 years; body mass index 31.6 +/- 7.9 kg/m 2 , range 18.5-54.7 kg/m 2), fasting TG levels and PH-LPL activity were determined. Visceral adipose tissue was measured by abdominal computed tomographic scan. Insulin resistance was determined by the insulin sensitivity index (S I). Subjects were divided into tertiles by S I . The range of S I in each tertile was 12.75 to 3.99, 3.87 to 2.20, 2.06 to 0.17 mU . L -1 . min -1 . Insulin resistance was defined as being in the third tertile. TG levels in the men and women were 82.2 +/- 35.5 versus 56.4 +/- 30.1 mg/dL, P < .001. There were no sex difference in PH-LPL activity (8.9 +/- 2.5 vs 9.6 +/- 3.2 mmol/h per liter, P = .30) or S I (3.65 +/- 2.59 vs 3.23 +/- 1.89 L . mU -1 . min -1 , P = .49). Although 47% of the subjects were obese, only 4% of subjects had hypertriglyceridemia (TG > or =150 mg/dL). By 2 separate analyses, PH-LPL was a major determinant of TG levels. First, there was a significant inverse correlation between PH-LPL activity and TG levels (men: r = -0.46, P < .001; women: r = -0.28, P = .046). Second, in the multiple regression analysis with TG as the dependent variable and PH-LPL, age, sex, S I , and visceral adipose tissue as independent variables, adjusted R 2 was 54% and the effect of PH-LPL on TG levels was highly significant(P < .001). However, insulin resistance did not appear to influence PH-LPL activity. This is demonstrated in 3 ways: first, PH-LPL activity was not different in the S I tertiles (9.10 +/- 2.75, 9.52 +/- 2.91, 9.13 +/- 2.89 mmol/h per liter, P = .78); the correlation between PH-LPL and S I was not significant (men: r = 0.09, P = .51; women: r = -0.03, P = .78), and a multiple regression with PH-LPL as the dependent variable and age, S I , body mass index, and sex as independent variables, adjusted R 2 was <2% and the contribution of S I was not significant (P = .53). Hence, in African Americans, increased PH-LPL activity is associated with a decrease in TG levels. The lack of an effect of insulin resistance on PH-LPL could allow LPL to clear TG even in the presence of insulin resistance and explain the coexistence of insulin resistance and normotriglyceridemia in African Americans.

Authors+Show Affiliations

Clinical Endocrinology Branch, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1612, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15988699

Citation

Sumner, Anne E., et al. "Normal Triglyceride Levels Despite Insulin Resistance in African Americans: Role of Lipoprotein Lipase." Metabolism: Clinical and Experimental, vol. 54, no. 7, 2005, pp. 902-9.
Sumner AE, Vega GL, Genovese DJ, et al. Normal triglyceride levels despite insulin resistance in African Americans: role of lipoprotein lipase. Metabolism. 2005;54(7):902-9.
Sumner, A. E., Vega, G. L., Genovese, D. J., Finley, K. B., Bergman, R. N., & Boston, R. C. (2005). Normal triglyceride levels despite insulin resistance in African Americans: role of lipoprotein lipase. Metabolism: Clinical and Experimental, 54(7), 902-9.
Sumner AE, et al. Normal Triglyceride Levels Despite Insulin Resistance in African Americans: Role of Lipoprotein Lipase. Metabolism. 2005;54(7):902-9. PubMed PMID: 15988699.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Normal triglyceride levels despite insulin resistance in African Americans: role of lipoprotein lipase. AU - Sumner,Anne E, AU - Vega,Gloria L, AU - Genovese,David J, AU - Finley,Karl B, AU - Bergman,Richard N, AU - Boston,Raymond C, PY - 2005/7/1/pubmed PY - 2005/8/24/medline PY - 2005/7/1/entrez SP - 902 EP - 9 JF - Metabolism: clinical and experimental JO - Metabolism VL - 54 IS - 7 N2 - Abstract Lipoprotein lipase (LPL), the enzyme responsible for hydrolyzing triglyceride (TG) in plasma lipoproteins, is a key regulator of plasma TG levels. In Caucasians, postheparin-LPL (PH-LPL) activity is impaired in the presence of insulin resistance and leads to elevated TG levels. However, African Americans are often both insulin-resistant and normotriglyceridemic. But in African Americans, the effect of insulin resistance on PH-LPL activity has not been studied. In African Americans, if insulin resistance is not associated with a decrease in PH-LPL activity, this could account for the simultaneous presence of insulin resistance and normotriglyceridemia. Therefore, our goal was to determine in African Americans the relationship between insulin resistance and PH-LPL activity. In a cross-sectional study of 107 nondiabetic African Americans (57 men and 50 women; age mean +/- SD, 35 +/- 8 years, range 22-50 years; body mass index 31.6 +/- 7.9 kg/m 2 , range 18.5-54.7 kg/m 2), fasting TG levels and PH-LPL activity were determined. Visceral adipose tissue was measured by abdominal computed tomographic scan. Insulin resistance was determined by the insulin sensitivity index (S I). Subjects were divided into tertiles by S I . The range of S I in each tertile was 12.75 to 3.99, 3.87 to 2.20, 2.06 to 0.17 mU . L -1 . min -1 . Insulin resistance was defined as being in the third tertile. TG levels in the men and women were 82.2 +/- 35.5 versus 56.4 +/- 30.1 mg/dL, P < .001. There were no sex difference in PH-LPL activity (8.9 +/- 2.5 vs 9.6 +/- 3.2 mmol/h per liter, P = .30) or S I (3.65 +/- 2.59 vs 3.23 +/- 1.89 L . mU -1 . min -1 , P = .49). Although 47% of the subjects were obese, only 4% of subjects had hypertriglyceridemia (TG > or =150 mg/dL). By 2 separate analyses, PH-LPL was a major determinant of TG levels. First, there was a significant inverse correlation between PH-LPL activity and TG levels (men: r = -0.46, P < .001; women: r = -0.28, P = .046). Second, in the multiple regression analysis with TG as the dependent variable and PH-LPL, age, sex, S I , and visceral adipose tissue as independent variables, adjusted R 2 was 54% and the effect of PH-LPL on TG levels was highly significant(P < .001). However, insulin resistance did not appear to influence PH-LPL activity. This is demonstrated in 3 ways: first, PH-LPL activity was not different in the S I tertiles (9.10 +/- 2.75, 9.52 +/- 2.91, 9.13 +/- 2.89 mmol/h per liter, P = .78); the correlation between PH-LPL and S I was not significant (men: r = 0.09, P = .51; women: r = -0.03, P = .78), and a multiple regression with PH-LPL as the dependent variable and age, S I , body mass index, and sex as independent variables, adjusted R 2 was <2% and the contribution of S I was not significant (P = .53). Hence, in African Americans, increased PH-LPL activity is associated with a decrease in TG levels. The lack of an effect of insulin resistance on PH-LPL could allow LPL to clear TG even in the presence of insulin resistance and explain the coexistence of insulin resistance and normotriglyceridemia in African Americans. SN - 0026-0495 UR - https://www.unboundmedicine.com/medline/citation/15988699/Normal_triglyceride_levels_despite_insulin_resistance_in_African_Americans:_role_of_lipoprotein_lipase_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0026049505000910 DB - PRIME DP - Unbound Medicine ER -