Impact of percent body fat on oral glucose tolerance testing: a cross-sectional study in 1512 obese children

Relationship between glucose metabolism and non-alcoholic fatty liver disease severity in morbidly obese women

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is an independent predictor of type 2 diabetes mellitus (T2DM). Insulin resistance and beta-cell dysfunction are involved in the pathogenesis of T2DM. Insulin resistance is associated with NAFLD but little is known about beta-cell dysfunction and NAFLD.

AIM

We tested whether NAFLD severity is associated with insulin sensitivity and beta-cell function in morbidly obese women.

SUBJECTS AND METHODS

We studied 61 Caucasian women aged 18-60 years without T2DM and with a body mass index ranging from 35.3 to 48.8 kg/m². The insulin sensitivity index (ISI) and the disposition index (DI) from oral glucose tolerance testing were used as measures of insulin sensitivity and beta-cell function, respectively. Fat was measured by dual-energy X-ray absorptiometry. Fatty liver was diagnosed by ultrasonography and ordinally coded as 0 = none, 1 = light, 2 = moderate, 3 = severe. Proportional-odds logistic regression was used to evaluate the association of NAFLD severity with log(e)ISI and log(e)DI with and without correction for total and truncal fat.

RESULTS

The odds of more severe vs. less severe NAFLD decreased for increasing log(e)ISI [odds ratio (OR) 0.40, 95 % CI 0.19-0.84, p < 0.05] and log(e)DI (OR 0.80, 95 % CI 0.69-0.92, p < 0.01). Neither total nor truncal fat had any effect on these associations.

CONCLUSION

In morbidly obese women, NAFLD severity is inversely associated with insulin sensitivity and beta-cell function. The association of NAFLD severity with beta-cell dysfunction is stronger than that with insulin resistance.

Is non-alcoholic fatty liver disease less frequent among women with Prader-Willi syndrome?

OBJECTIVE

Patients with Prader-Willi syndrome (PWS) have been hypothesized to be at lower risk of non-alcoholic fatty liver disease (NAFLD) because of higher insulin sensitivity. However, PWS patients have a peculiar body composition, i.e. higher fat mass and lower fat-free mass, which may confound such associations. We evaluated whether NAFLD is less frequent in PWS than in non-PWS women matched on percent body fat (PBF).

METHODS

PBF was measured by dual-energy X-ray absorptiometry. Liver fat was assessed by ultrasonography. Insulin sensitivity and beta-cell function were evaluated by oral glucose tolerance testing. Coarsened exact matching (CEM) was used to match PWS and non-PWS women on PBF. General and generalized linear models taking CEM into account were used to perform comparisons between PWS and non-PWS women.

RESULTS

20 women with PWS were matched to 27 women without PWS on the basis of PBF (mean 53 vs. 54%, p = 0.6). Insulin sensitivity and beta-cell function were similar in the two groups. However, the prevalence of NAFLD was 25% in PWS versus 59% in non-PWS women (p = 0.04).

CONCLUSION

NAFLD is less frequent in PWS than in non-PWS women but this finding is not associated with higher insulin sensitivity.