Energy Balance and Prostate Cancer by Elizabeth A. Platz & Nathan A. Berger

Author:Elizabeth A. Platz & Nathan A. Berger
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Obesity

Positive associations between overall obesity, expressed by BMI or abdominal obesity, with circulating levels of insulin and C-peptide have been reported in several cross-sectional studies [56, 80–82]. Several studies also examined cross-sectionally how IGF-1 is associated with obesity. However, the findings observed are quite heterogeneous. In an analysis of NHANES III data, IGF-1 decreased with increasing BMI and waist circumference [83]. They did, however, not examine the association with IGFBP-3 or the ratio as an indicator of free IGF-1 concentration. In the CARDIA study , higher BMI, but not larger waist circumference, was associated with lower IGF-1; neither BMI nor waist circumference was related to IGFBP-3 concentrations [60]. Among 1142 male participants in the EPIC cohort, IGF-1 concentrations were associated with BMI in an “inverse” U-shaped manner: men with BMI of 26–27 kg/m2 had the highest IGF-1 serum levels, but IGFBP-3 concentrations were not associated with BMI [84]. This pattern has also been reported in a Swedish study [85]. In a recent Danish study including 1493 men, circulating IGF-1 levels were inversely associated with all anthropometric markers adjusting for age, alcohol consumption, smoking and physical activity [86]; IGFBP-3 concentrations were not evaluated. In a German cohort, inverse linear and quadratic associations between anthropometric parameters and serum IGF-1 were found. Additionally, men with high waist circumference more often had low serum IGF-1 and less often had high serum IGF-1 levels compared to men with low waist circumference [87]. In a study among Chinese men, IGF-1 was positively associated with BMI, as was IGFBP-3 [39]. Other studies observed no associations of IGF-1 and/or IGFBP-3 concentration with obesity (for example, [88]).

Numerous studies have shown a cross-sectional association between obesity and blood lipids [89, 90]. Both overall obesity and abdominal obesity tend to be positively associated with total and LDL cholesterol as well as triglyceride concentrations, but inversely with HDL cholesterol.

Variations in the fatty acid synthase (FASN ) gene in relation to differences in BMI have been examined in several studies. In non-diabetic Pima Indians, a Val1483Ile polymorphism (GTC to ATC) was associated with percentage of body fat. Compared with homozygotes for the Val variant, subjects with Ile/x had a lower mean percentage of body fat (30 ± 1% vs. 33 ± 1%, P = 0.002; adjusted for age, sex, and family membership), resulting in a lower mean carbohydrate oxidation rate [91]. In a German study, Caucasians boys with Ile/Val genotype compared to Val/Val had a lower BMI standard deviation score (SDS; −0.36 ± 0.29 vs 0.09 ± 0.05, P < 0.05), whereas the opposite was observed in girls (0.48 ± 0.19 vs 0.09 ± 0.05, P < 0.05) [92]. A third study, conducted among mostly Caucasian women, found that two SNPs in FASN were associated with obesity [93]. Lastly, a US study showed that men with the homozygous AA (vs. GG) variant of rs1127678 in FASN had an approximately 2% higher BMI [94]. A German study including 196 lean or obese participants observed that increased FASN gene expression in adipose tissue was linked

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