Parental Obesity and Offspring Serum Alanine and Aspartate Aminotransferase Levels: The Framingham Heart Study
2008; Elsevier BV; Volume: 134; Issue: 4 Linguagem: Inglês
10.1053/j.gastro.2008.01.037
ISSN1528-0012
AutoresRohit Loomba, Shih‐Jen Hwang, Christopher J. O’Donnell, R. Curtis Ellison, Ramachandran S. Vasan, Ralph B. D’Agostino, Tiebing Liang, Caroline S. Fox,
Tópico(s)Diet, Metabolism, and Disease
ResumoBackground & Aims: Obesity is an important correlate of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. We sought to examine the relations between parental obesity and the serum ALT and AST levels among offspring in a community-based sample. Methods: Participants (n = 1732) of the Framingham Offspring Study (50% women; mean age, 42 years) who had serum ALT and AST measurements and both parents in the original Framingham cohort were studied. Study participants were grouped into early-onset parental obesity (n = 193) (at least one parent obese), later-onset parental obesity (n = 460), and no parental obesity (n = 1079) subgroups. The association between elevated ALT or AST levels and parental obesity was tested using generalized estimating equations to account for familial correlations. Results: In multivariable analysis including adjustment for offspring obesity, significantly higher ALT levels were observed among individuals with paternal early-onset obesity as compared with those without paternal obesity (P = .02). Offspring with early-onset paternal obesity were more likely to have elevated ALT levels compared with those without paternal obesity (odds ratio, 1.75; 95% confidence interval, 1.06–2.89; P = .03). There was no association with elevated ALT levels among offspring with maternal early-onset obesity (odds ratio, 1.10; 95% confidence interval, 0.76–1.59; P = .61). There was no association between parental obesity and serum AST levels. Conclusions: Early-onset paternal obesity, but not maternal obesity, increases the odds of elevated serum ALT levels in offspring, suggesting a predisposition to developing elevated serum ALT levels that may be mediated through familial early-onset obesity. Background & Aims: Obesity is an important correlate of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. We sought to examine the relations between parental obesity and the serum ALT and AST levels among offspring in a community-based sample. Methods: Participants (n = 1732) of the Framingham Offspring Study (50% women; mean age, 42 years) who had serum ALT and AST measurements and both parents in the original Framingham cohort were studied. Study participants were grouped into early-onset parental obesity (n = 193) (at least one parent obese), later-onset parental obesity (n = 460), and no parental obesity (n = 1079) subgroups. The association between elevated ALT or AST levels and parental obesity was tested using generalized estimating equations to account for familial correlations. Results: In multivariable analysis including adjustment for offspring obesity, significantly higher ALT levels were observed among individuals with paternal early-onset obesity as compared with those without paternal obesity (P = .02). Offspring with early-onset paternal obesity were more likely to have elevated ALT levels compared with those without paternal obesity (odds ratio, 1.75; 95% confidence interval, 1.06–2.89; P = .03). There was no association with elevated ALT levels among offspring with maternal early-onset obesity (odds ratio, 1.10; 95% confidence interval, 0.76–1.59; P = .61). There was no association between parental obesity and serum AST levels. Conclusions: Early-onset paternal obesity, but not maternal obesity, increases the odds of elevated serum ALT levels in offspring, suggesting a predisposition to developing elevated serum ALT levels that may be mediated through familial early-onset obesity. See Ohki T et al on page 459 in CGH. See Ohki T et al on page 459 in CGH. Obesity is an important global public health problem1Seidell J.C. Obesity, insulin resistance and diabetes—a worldwide epidemic.Br J Nutr. 2000; 83: S5-S8PubMed Google Scholar, 2Yoon K.H. Lee J.H. Kim J.W. et al.Epidemic obesity and type 2 diabetes in Asia.Lancet. 2006; 368: 1681-1688Abstract Full Text Full Text PDF PubMed Scopus (1225) Google Scholar, 3Ogden C.L. Carroll M.D. Curtin L.R. et al.Prevalence of overweight and obesity in the United States, 1999-2004.JAMA. 2006; 295: 1549-1555Crossref PubMed Scopus (7494) Google Scholar, 4Li C. Ford E.S. McGuire L.C. et al.Increasing trends in waist circumference and abdominal obesity among U.S. adults.Obesity (Silver Spring). 2007; 15: 216-224Crossref PubMed Scopus (235) Google Scholar and is a modifiable risk factor for morbidity and mortality.5Peters E.T. Seidell J.C. 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Based on the National Health and Nutrition Examination Survey data, up to 7% of the adult US population has unexplained elevated ALT levels,9Ioannou G.N. Boyko E.J. Lee S.P. The prevalence and predictors of elevated serum aminotransferase activity in the United States in 1999–2002.Am J Gastroenterol. 2006; 101: 76-82Crossref PubMed Scopus (267) Google Scholar most likely due to nonalcoholic fatty liver disease (NAFLD).9Ioannou G.N. Boyko E.J. Lee S.P. The prevalence and predictors of elevated serum aminotransferase activity in the United States in 1999–2002.Am J Gastroenterol. 2006; 101: 76-82Crossref PubMed Scopus (267) Google Scholar NAFLD is a spectrum of liver disease ranging from benign steatosis to nonalcoholic steatohepatitis (NASH), a progressive form of NAFLD that may lead to chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma.10Neuschwander-Tetri B.A. Nonalcoholic steatohepatitis and the metabolic syndrome.Am J Med Sci. 2005; 330: 326-335Crossref PubMed Scopus (168) Google Scholar The association between elevated ALT levels, obesity, and metabolic risk factors including diabetes has been recognized,11Bedogni G. Miglioli L. Masutti F. et al.Prevalence of and risk factors for nonalcoholic fatty liver disease: the Dionysos nutrition and liver study.Hepatology. 2005; 42: 44-52Crossref PubMed Scopus (1063) Google Scholar, 12Meltzer A.A. Everhart J.E. 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Association between diabetes and elevated serum alanine aminotransferase activity among Mexican Americans.Am J Epidemiol. 1997; 146: 565-571Crossref PubMed Scopus (59) Google Scholar, 15Ioannou G.N. Boyko E.J. Lee S.P. The prevalence and predictors of elevated serum aminotransferase activity in the United States in 1999-2002.Am J Gastroenterol. 2006; 101: 76-82Crossref PubMed Scopus (151) Google Scholar, 16Browning J.D. Szczepaniak L.S. Dobbins R. et al.Prevalence of hepatic steatosis in an urban population in the United States: impact of ethnicity.Hepatology. 2004; 40: 1387-1395Crossref PubMed Scopus (3048) Google Scholar Familial clustering of fatty liver, NASH, and cryptogenic cirrhosis has been reported, further suggesting that genetic factors may play a role in the pathogenesis of NAFLD.17Browning J.D. Kumar K.S. Saboorian M.H. et al.Ethnic differences in the prevalence of cryptogenic cirrhosis.Am J Gastroenterol. 2004; 99: 292-298Crossref PubMed Scopus (196) Google Scholar, 18Struben V.M. Hespenheide E.E. Caldwell S.H. Nonalcoholic steatohepatitis and cryptogenic cirrhosis within kindreds.Am J Med. 2000; 108: 9-13Abstract Full Text Full Text PDF PubMed Scopus (272) Google Scholar, 19Willner I.R. Waters B. Patil S.R. et al.Ninety patients with nonalcoholic steatohepatitis: insulin resistance, familial tendency, and severity of disease.Am J Gastroenterol. 2001; 96: 2957-2961Crossref PubMed Google Scholar Data from a Danish twin study suggest that the heritability estimate of ALT is between 0.33 and 0.48, which is independent of body mass index (BMI) and alcohol consumption.20Bathum L. Petersen H.C. Rosholm J.U. et al.Evidence for a substantial genetic influence on biochemical liver function tests: results from a population-based Danish twin study.Clin Chem. 2001; 47: 81-87PubMed Google Scholar Therefore, the goal of this study is to examine the association of parental obesity with serum levels of ALT and AST in offspring. To evaluate the contribution of genetic factors, we investigated whether early-onset parental obesity is associated with elevated ALT and AST levels. We hypothesized that offspring of parents with early-onset or general obesity are more likely to have higher ALT or AST levels than offspring of nonobese parents. The Framingham Heart Study is a prospective epidemiological study of cardiovascular disease and its risk factors that was started in 1948 by recruiting 5209 men and women between the ages of 30 and 62 years from the residents of Framingham, Massachusetts. Participants are followed up with biennial examinations.21Cupples L.A. DARBSome risk factors related to the annual incidence of cardiovascular disease and death using pooled repeated biennial measurements: Framingham Study, 30-year follow-up.in: Kannel W.B. Polf P.A. Garrison R.J. The Framingham Heart Study: an epidemiological investigation of cardiovascular disease. Government Printing Office, Washington, DC1987Google Scholar In 1971, 5124 offspring and offspring spouses were recruited as an extension of the Framingham Heart Study and classified as the Framingham Offspring Study cohort.22Feinleib M. Kannel W.B. Garrison R.J. et al.The Framingham Offspring Study Design and preliminary data.Prev Med. 1975; 4: 518-525Crossref PubMed Scopus (720) Google Scholar The study participants for the current study were derived from the Framingham Offspring Study. Written informed consent was obtained from all the participants, and the Institutional Review Board of Boston Medical Center approved the research protocol. The details of the cohort, selection criteria, and purpose of the Framingham Offspring Study have been reported previously.22Feinleib M. Kannel W.B. Garrison R.J. et al.The Framingham Offspring Study Design and preliminary data.Prev Med. 1975; 4: 518-525Crossref PubMed Scopus (720) Google Scholar Only offspring participants with data available for both parents were included to minimize misclassification of parental obesity status. Offspring participants with both parents in the cohort were similar to offspring without both parents in the cohort with the exception of age, because participants with both parents in the cohort were on average 4 years younger (P < .001). Among offspring participants who attended the second offspring examination (1978–1982; n = 3867), 1887 had both parents as members of the original cohort of the Framingham Heart Study. Additionally, we excluded 155 participants for the following reasons: unavailability of serum ALT or AST levels (n = 89), serum ALT or AST level >120 IU/L (n = 13), BMI <18.5 kg/m2 (n = 29), missing covariate data (n = 18), and parents with maximum BMI <18.5 kg/m2 (n = 6). Parental obesity was defined as a BMI of 30 kg/m2 or more on at least 2 occasions during the entire follow-up of the original cohort. Early-onset parental obesity was defined empirically as the 25th percentile of the age at the first obesity among these obese fathers and mothers (41 years in men and 45 years in women). The study participants were hence grouped into 3 categories: (1) early-onset parental obesity, (2) later-onset parental obesity, and (3) no parental obesity. Serum ALT and AST levels were measured on fasting morning samples using the kinetic method (Beckman Liquid-Stat Reagent Kit).23Henry R.J. Chiamori N. Golub O.J. et al.Revised spectrophotometric methods for the determination of glutamic-oxalacetic transaminase, glutamic-pyruvic transaminase, and lactic acid dehydrogenase.Am J Clin Pathol. 1960; 34: 381-398Crossref PubMed Google Scholar Coefficients of variation for ALT and AST were 8.3% and 10.7%, respectively. We defined elevated ALT level using the cut point of serum ALT level ≥30 IU/L in men and ≥19 IU/L in women as suggested by Prati et al.24Prati D. Taioli E. Zanella A. et al.Updated definitions of healthy ranges for serum alanine aminotransferase levels.Ann Intern Med. 2002; 137: 1-10Crossref PubMed Scopus (1191) Google Scholar, 25Chang Y. Ryu S. Sung E. et al.Higher concentrations of alanine aminotransferase within the reference interval predict nonalcoholic fatty liver disease.Clin Chem. 2007; 53: 686-692Crossref PubMed Scopus (175) Google Scholar We used the same cut-off level for serum AST. Details regarding the methods of risk factor measurement and laboratory analysis have been described elsewhere.21Cupples L.A. DARBSome risk factors related to the annual incidence of cardiovascular disease and death using pooled repeated biennial measurements: Framingham Study, 30-year follow-up.in: Kannel W.B. Polf P.A. Garrison R.J. The Framingham Heart Study: an epidemiological investigation of cardiovascular disease. Government Printing Office, Washington, DC1987Google Scholar BMI was defined as weight (kilograms) divided by square of the height (meters). Participants with systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg (average of 2 readings recorded by a study investigator) or receiving medications for the treatment of hypertension were classified as hypertensive. Fasting lipid measures included serum triglyceride, total cholesterol, and high-density lipoprotein (HDL) cholesterol. Diabetes was defined as a fasting plasma glucose level ≥7 mmol/L (126 mg/dL) or treatment with either insulin or a hypoglycemic agent. Participants who reported smoking during the previous year before the examination were reported as current smokers. Excess alcohol use was defined as 7 or more drinks a week in women or 14 or more drinks a week in men. In addition, an intensive chart review of all subjects was used to identify key words suggesting alcohol dependence or other alcohol abuse. Cardiovascular disease was defined by standard Framingham Heart Study criteria as any of the following: new-onset angina, fatal and nonfatal myocardial infarction or stroke, transient ischemic attack, heart failure, or intermittent claudication. Logarithmically transformed serum ALT and AST levels were used in the analyses because of their skewed distributions. The generalized estimating equation (GEE) model was used to account for familial correlation. The statistical significance of differences in ALT and AST values among the 3 exposure groups (early-onset parental obesity, later-onset parental obesity, no parental obesity [referent]) was tested using GEE by generating least square means of the log-transformed ALT or AST levels. We also grouped individuals by having elevated ALT or AST levels and applied GEE using multivariable logistic regression to generate the odds of elevated ALT and AST levels in individuals with early-onset parental obesity or later-onset parental obesity relative to those without a parental history of obesity (referent group). In addition to parental obesity, the significance of the association for obesity in fathers (paternal history of obesity) or mothers (maternal history of obesity) was examined. We tested the hypothesis by adjusting for (1) age and sex and (2) multiple covariates including age, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total/HDL cholesterol ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and prevalent cardiovascular disease. Secondary analyses were conducted by excluding offspring participants with obesity (n = 158) to assess whether the observed findings were independent of offspring obesity. Offspring with excess alcohol use (n = 190), as defined by more than 7 drinks per week (men) or 14 drinks per week (women) or indication of alcohol dependence or abuse identified from an extensive chart review, were also excluded. A 2-sided P value of <.05 was consider significant. SAS version 8.1 (SAS Institute, Inc, Cary, NC) was used for all analyses. A total of 1732 offspring cohort participants were included in this study with a mean age of 42 years, and half were women. Nearly one tenth had a history of early-onset parental obesity (n = 193), and 27% had a history of later-onset parental obesity (n = 460); study participant characteristics are presented in Table 1. Offspring in the early-onset parental obesity group were younger, had higher BMI, had higher serum triglyceride and serum ALT levels, and had lower serum HDL levels as compared with offspring without parental obesity, whereas few differences existed for later-onset obesity as compared with no parental obesity.Table 1Characteristics of Offspring Participants by Parental Obesity Status Based on at Least One Obese ParentEarly-onset parental obesity (n = 193)Later-onset parental obesity (n = 460)No parental obesity (referent group) (n = 1079)P valueaEarly-onset parental obesity versus no parental obesity.P valuebLater-onset parental obesity versus no parental obesity.Age (y)38 (7)42 (10)43 (9)<.001.19Women (%)465251.21.80BMI (kg/m2)27.1 (5.2)26.1 (4.5)25.0 (3.8)<.001<.001Systolic blood pressure (mm Hg)119 (14)121 (16)121 (16).39.47Total cholesterol level (mg/dL)196 (34)199 (37)201 (38).45.70HDL cholesterol level (mg/dL)47 (13)48 (13)49 (13).03.38Total/HDL cholesterol ratio4.6 (1.6)4.5 (1.6)4.4 (1.6).03.27Triglyceride level (mg/dL)135 (79)131 (70)128 (73).03.23Alcohol intake (drinks/wk)3.2 (4.1)3.8 (5.8)3.9 (5.2).38.83Diabetes (%)022N/AN/AHypertension treatment (%)6107.21.03Current smoking (%)433835.17.39Cardiovascular disease (%)643.05.16ALT level (IU/L)cALT and AST levels are presented as median (25th to 75th percentiles).25 (19–35)22 (16–31)22 (16–32).01.23AST level (IU/L)cALT and AST levels are presented as median (25th to 75th percentiles).20 (12–26)19 (14–25)19 (14–25).43.31Elevated ALT level, % (n)dElevated ALT or AST level is defined as ≥30 IU/L in men and ≥19 IU/L in women.52 (100)42 (195)43 (459).006.96Elevated AST level, % (n)dElevated ALT or AST level is defined as ≥30 IU/L in men and ≥19 IU/L in women.30 (58)26 (119)27 (291).18.68NOTE. P values were abstracted from GEE model adjusted for age, sex, and familial correlation comparing participants with parental (early-onset or later-onset) obesity with those without parental obesity. Data are presented as mean (SD) for continuous variables or percent (n) for categorical variables.N/A, not applicable.a Early-onset parental obesity versus no parental obesity.b Later-onset parental obesity versus no parental obesity.c ALT and AST levels are presented as median (25th to 75th percentiles).d Elevated ALT or AST level is defined as ≥30 IU/L in men and ≥19 IU/L in women. Open table in a new tab NOTE. P values were abstracted from GEE model adjusted for age, sex, and familial correlation comparing participants with parental (early-onset or later-onset) obesity with those without parental obesity. Data are presented as mean (SD) for continuous variables or percent (n) for categorical variables. N/A, not applicable. In offspring with early-onset parental obesity, 41% had paternal obesity, 64% had maternal obesity, and 6% had both. In offspring with later-onset parental obesity, 46% had paternal obesity, 69% had maternal obesity, and 0% had both maternal and paternal obesity. The Pearson correlation coefficient between maternal BMI and paternal BMI was 0.35. Age- and sex-adjusted log ALT levels were higher among participants with at least one parent with early-onset obesity (Table 2) as compared with those without parental obesity (3.21 ± 0.04 vs 3.08 ± 0.02; P = .001). Age- and sex-adjusted log ALT levels remained statistically significant when participants with early-onset maternal or paternal obesity were compared with those without paternal or maternal obesity. The multivariable adjusted log ALT levels were significantly higher only among participants with paternal obesity as compared with those without paternal obesity (3.21 ± 0.06 vs 3.08 ± 0.01; P = .02). Similar comparison with respective referent groups for maternal and at least one parent obese models did not achieve statistical significance. No significant differences were observed in any of the models when participants with later-onset obesity were compared with those without parental obesity. No significant differences in AST levels in any of the models in the 3 exposure categories were observed.Table 2Log-Transformed ALT and AST Values by Parental History of ObesityEarly-onset parental obesity (n = 193)Later-onset parental obesity (n = 460)No parental obesity (referent group) (n = 1079)P valueaEarly-onset parental obesity versus no parental obesity.P valuebLater-onset parental obesity versus no parental obesity.ALT Father Age-sex model3.27 (0.06)3.10 (0.03)3.08 (0.02).001.44 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.3.21 (0.06)3.08 (0.03)3.08 (0.01).02.99 Mother Age-sex model3.19 (0.04)3.07 (0.03)3.08 (0.02).02.72 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.3.15 (0.04)3.05 (0.03)3.10 (0.02).22.14 At least one affected parent Age-sex model3.21 (0.04)3.06 (0.03)3.08 (0.02).001.39 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.3.17 (0.03)3.03 (0.03)3.10 (0.02).07.05AST Father Age-sex model3.00 (0.05)2.93 (0.03)2.91 (0.01).06.41 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.2.99 (0.05)2.92 (0.03)2.91 (0.01).10.63 Mother Age-sex model2.94 (0.04)2.92 (0.03)2.91 (0.01).51.70 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.2.93 (0.04)2.91 (0.02)2.90 (0.01).69.83 At least one affected parent Age-sex model2.96 (0.03)2.91 (0.02)2.90 (0.02).15.72 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease.2.95 (0.03)2.90 (0.02)2.91 (0.02).30.77NOTE. Least squares of mean (SE) of log-transformed serum ALT and AST values are presented. Results obtained from GEE are adjusted for familial correlation.a Early-onset parental obesity versus no parental obesity.b Later-onset parental obesity versus no parental obesity.c Age, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption, and cardiovascular disease. Open table in a new tab NOTE. Least squares of mean (SE) of log-transformed serum ALT and AST values are presented. Results obtained from GEE are adjusted for familial correlation. Age- and sex-adjusted odds ratio (OR) of elevated serum ALT level was higher in offspring with both paternal early-onset obesity as compared with no paternal obesity (Table 3; OR, 2.04, 95% confidence interval [CI], 1.29–3.24, P = .005) and early-onset obesity in at least one parent compared with no parental obesity (OR, 1.52; 95% CI, 1.13–2.06; P = .006). However, statistical significance was not observed in models examining maternal early-onset obesity as compared with no maternal obesity (OR, 1.33; 95% CI, 0.95–1.85; P = .09). In multivariable models, participants with paternal early-onset obesity had higher serum ALT levels (Table 3; OR, 1.75; 95% CI, 1.06–2.89; P = .03) relative to those without paternal obesity. Early-onset paternal obesity was associated with ALT elevation independent of maternal obesity in multivariable-adjusted models (OR, 1.72; 95% CI, 1.02–2.69; P = .03). Those with a history of maternal obesity or at least one obese parent did not have elevated ALT levels, with an OR of 1.10 (95% CI, 0.76–1.59; P = .61) and an OR of 1.25 (95% CI, 0.90–1.74; P = .18), respectively, when compared with offspring without maternal obesity or those without either parent with obesity, respectively. There were no significant differences in the odds of elevated ALT levels in participants with later-onset parental obesity when compared with offspring without parental obesity (Table 3). The odds of elevated serum AST levels in the offspring did not differ in the exposure groups (early-onset parental obesity and later-onset parental obesity) when compared with the offspring without parental obesity.Table 3OR of Elevated ALT and AST Levels With or Without Adjustment Grouped by Parental Obesity StatusEarly-onset versus no parental obesityLater-onset versus no parental obesityOR (95% CI)P valueaEarly onset versus no parental obesity.OR (95% CI)P valuebLater-onset versus no parental obesity.ALT Father Age-sex model2.04 (1.29–3.24).0051.05 (0.79–1.39).76 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.75 (1.06–2.89).030.93 (0.68–1.27).66 Mother Age-sex model1.33 (0.95–1.85).091.05 (0.82–1.35).68 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.10 (0.76–1.59).610.91 (0.70–1.18).49 At least one affected parent Age-sex model1.52 (1.13–2.06).0061.01 (0.80–1.26).97 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.25 (0.90–1.74).180.88 (0.69–1.12).29AST Father Age-sex model1.26 (0.78–2.04).340.94 (0.69–1.29).71 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.18 (0.73–1.91).490.91 (0.65–1.26).56 Mother Age-sex model1.24 (0.81–1.74).280.95 (0.72–1.26).73 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.14 (0.75–1.71).540.86 (0.65–1.16).33 At least one affected parent Age-sex model1.28 (0.92–1.80).150.95 (0.73–1.23).68 Multivariable modelcAge, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease.1.17 (0.82–1.66).390.87 (0.66–1.14).32NOTE. The analysis is based on the GEE model adjusted for familial correlation. The referent group is either offspring without a paternal, maternal, or parental history of obesity for father, mother, and at least one affected parent model, respectively.a Early onset versus no parental obesity.b Later-onset versus no parental obesity.c Age, sex, diabetes, BMI, systolic blood pressure, hypertension treatment, total cholesterol/HDL ratio, triglyceride level, smoking status, total alcohol consumption (drinks/week), and cardiovascular disease. Open table in a new tab NOTE. The analysis is based on the GEE model adjusted for familial correlation. The referent group is either offspring without a paternal, maternal, or parental history of obesity for father, mother, and at least one affected parent model, respectively. After excluding obese offspring, the overall findings were essentially unchanged, although in these secondary analyses the multivariable adjusted ORs were somewhat strengthened for the association between paternal early-onset obesity and ALT (see Supplementary Table 1; see supplemental material online at www.gastrojournal.org). Among individuals without excess alcohol consumption or abuse, the results were not substantially different (data not shown). In this community-based sample of white adults, we found that a paternal history of early-onset obesity is associated with a higher OR of elevated serum ALT levels in offspring. This relation is independent of the offspring's BMI and persists among nonobese offspring. Moreover, early-onset paternal obesity but not maternal obesity was associated with elevated serum ALT levels in the offspring. On the contrary, serum AST levels were not associated with parental obesity status. NAFLD is now considered the most common cause of serum ALT elevations in the US population.9Ioannou G.N. Boyko E.J. Lee S.P. The prevalence and predictors of elevated serum aminotransferase activity in the United States in 1999–2002.Am J Gastroenterol. 2006; 101: 76-82Crossref PubMed Scopus (267) Google Scholar Previous studies have shown that there is familial clustering of factors that may predispose to the development of NAFLD, NASH, and cryptogenic cirrhosis.18Struben V.M. Hespenheide E.E. Caldwell S.H. Nonalcoholic steatohepatitis and cryptogenic cirrhosis within kindreds.Am J Med. 2000; 108: 9-13Abstract Full Text Full Text PDF PubMed Scopus (272) Google Scholar, 19Willner I.R. Waters B. Patil S.R. et al.Ninety patients with nonalcoholic steatohepatitis: insulin resistance, familial tendency, and severity of disease.Am J Gastroenterol. 2001; 96: 2957-2961Crossref PubMed Google Scholar, 26Abdelmalek M.F. Liu C. Shuster J. et al.Familial aggregation of insulin resistance in first-degree relatives of patients with nonalcoholic fatty liver disease.Clin Gastroenterol Hepatol. 2006; 4: 1162-1169Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar Struben et al reported increased prevalence of NASH or cryptogenic cirrhosis or both in 7 of 8 kindreds.18Struben V.M. Hespenheide E.E. Caldwell S.H. Nonalcoholic steatohepatitis and cryptogenic cirrhosis within kindreds.Am J Med. 2000; 108: 9-13Abstract Full Text Full Text PDF PubMed Scopus (272) Google Scholar Willner et al showed that the prevalence of NAFLD is higher in first-degree relatives of patients with NASH.19Willner I.R. Waters B. Patil S.R. et al.Ninety patients with nonalcoholic steatohepatitis: insulin resistance, familial tendency, and severity of disease.Am J Gastroenterol. 2001; 96: 2957-2961Crossref PubMed Google Scholar Both of these findings suggest that NAFLD and elevated serum ALT levels may have an underlying genetic susceptibility, particularly in the setting of obesity.27Merriman R.B. Aouizerat B.E. Bass N.M. Genetic influences in nonalcoholic fatty liver disease.J Clin Gastroenterol. 2006; 40: S30-S33PubMed Google Scholar, 28Day C.P. Genes or environment to determine alcoholic liver disease and non-alcoholic fatty liver disease.Liver Int. 2006; 26: 1021-1028Crossref PubMed Scopus (150) Google Scholar A recent study by Kazumi et al showed an association between parental BMI and elevated serum ALT levels in their male offspring.29Kazumi T. Kawaguchi A. Yoshino G. Associations of middle-aged mother's but not father's body mass index with 18-year-old son's waist circumferences, birth weight, and serum hepatic enzyme levels.Metabolism. 2005; 54: 466-470Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar Contrary to our findings, this study reported that maternal rather than paternal BMI was associated with elevated ALT levels in Japanese men. The primary difference between this prior study and ours, in addition to being conducted in a sample of men from Japan, classified parental BMI exposure based on offspring recall. In our study, detailed information regarding measurement of parental BMI during a physician visit was obtained. Previous studies have shown that patient recall can lead to misclassification of exposure status. Therefore, differences in age, sex, race, and parental BMI may contribute to the disparate findings between these studies. Our findings suggest that there may be a familial component to ALT levels, and in particular, this predisposition may be mediated through early-onset familial obesity. Obesity has a strong familial and genetic component.14Rankinen T. Zuberi A. Chagnon Y.C. et al.The human obesity gene map: the 2005 update.Obesity (Silver Spring). 2006; 14: 529-644Crossref PubMed Scopus (935) Google Scholar Early-onset or premature occurrence of a disease condition may be more associated with an underlying genetic susceptibility. Therefore, these data support a potential mechanism of elevated ALT level. Several genes have been implicated in the development of early-onset obesity. A missense mutation in human pro-opiomelanocortin (POMC) gene30Delplanque J. Barat-Houari M. 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Kojima H. et al.Leptin-mediated neovascularization is a prerequisite for progression of nonalcoholic steatohepatitis in rats.Hepatology. 2006; 44: 983-991Crossref PubMed Scopus (135) Google Scholar Our findings raise the possibility that genes involved in the pathogenesis of early-onset obesity may also be associated with abnormal ALT levels. However, we cannot rule out the possibility that shared environmental and unmeasured behavioral practices could have contributed to this finding. Our findings were also notable for a stronger effect in the presence of a paternal history of early-onset obesity. One potential explanation may be that serum ALT is linked to genes on the Y-chromosome or X-linked conditions. An additional explanation may have to do with gene imprinting or telomere length, both of which have been suggested as a mechanism of paternal mode of inheritance.37Reik W. Walter J. Evolution of imprinting mechanisms: the battle of the sexes begins in the zygote.Nat Genet. 2001; 27: 255-256Crossref PubMed Scopus (192) Google Scholar, 38Nordfjall K. Larefalk A. Lindgren P. et al.Telomere length and heredity: indications of paternal inheritance.Proc Natl Acad Sci U S A. 2005; 102: 16374-16378Crossref PubMed Scopus (167) Google Scholar However, these hypotheses are speculative and need to be explored in future studies. Our results showed association for ALT and not AST. This was not entirely surprising because ALT has been shown to correlate better with obesity.39Salvaggio A. Periti M. Miano L. et al.Body mass index and liver enzyme activity in serum.Clin Chem. 1991; 37: 720-723PubMed Google Scholar Furthermore, elevations of serum AST level are more sensitive to alcohol consumption as compared with ALT, which is usually associated with NAFLD.40Kojima H. Sakurai S. Uemura M. et al.Difference and similarity between non-alcoholic steatohepatitis and alcoholic liver disease.Alcohol Clin Exp Res. 2005; 29: 259S-263SCrossref PubMed Scopus (41) Google Scholar Lastly, serum ALT is a more specific marker of liver injury than serum AST.41Panteghini M. Aspartate aminotransferase isoenzymes.Clin Biochem. 1990; 23: 311-319Crossref PubMed Scopus (80) Google Scholar, 42Guzman J. Petty R.E. Malleson P.N. Monitoring disease activity in juvenile dermatomyositis: the role of von Willebrand factor and muscle enzymes.J Rheumatol. 1994; 21: 739-743PubMed Google Scholar Strengths of our study include the use of a well-characterized large community-based sample. Parental adiposity status was obtained from routine Framingham Heart Study clinic examinations and was not based on offspring self-report. We were able to account for potentially important confounding variables that are known to be related to elevated serum ALT levels. Our study has several limitations. First, our sample was exclusively white; thus, the generalizability of these findings to other races or ethnic groups is uncertain. Second, the study sample included only offspring with both parents in the Framingham Heart Study. This was necessary to minimize bias due to misclassification of parental obesity status. Third, parental serum ALT and AST levels were not measured. Therefore, we cannot exclude the possibility that parents with early-onset obesity also had abnormal ALT or AST levels. Information on other liver diseases, such as viral hepatitis or autoimmune or metabolic liver disease and their risk factors, was not available, and therefore these conditions could not be excluded as a cause of ALT elevations. To limit potential bias, we excluded individuals who might have these conditions by restricting our study sample to offspring with ALT and AST levels <120 IU/L. These individuals were excluded because higher levels of serum ALT and AST are more likely to be associated with acute liver injury that may be related to factors such as drug-induced liver injury and acute viral hepatitis and not NAFLD. Nonetheless, inclusion of these individuals in our study would result in misclassification and would bias the results toward the null hypothesis. Therefore, it is unlikely that this issue contributes to our findings. Lastly, we did not have information on central obesity or measures of insulin resistance, 2 factors that could potentially mediate our findings. Our findings support the hypothesis that familial factors may play a role in the risks of elevated serum ALT levels in the general population. Further, this association may be mediated through early-onset obesity. It is possible that genes that associate with early-onset obesity may also be associated with elevated ALT levels. Future studies should specifically examine the relations of potential candidate genes, elevated ALT levels, and NAFLD. However, it is important to recognize that our findings do not establish a causal relationship between genetic factors and the development of elevated serum ALT levels or NAFLD. These results support the need for further studies to establish whether individuals with early-onset parental obesity and elevated serum ALT levels are at a higher risk for developing progressive liver disease such as NASH. Further research will also be important to identify whether these individuals are also at increased risk for developing metabolic complications of both obesity and NAFLD. These results need to be validated in other family studies to further understand the role of genetic and shared environmental factors on susceptibility to developing elevated serum ALT levels. A history of early-onset paternal obesity, but not general parental obesity, increases the odds of elevated serum ALT levels in offspring, suggesting a genetic predisposition to developing elevated serum ALT levels and perhaps NAFLD. Familial factors may be involved in the pathogenesis of elevated serum ALT levels.
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