Liver and pancreatic fat content and metabolism in healthy monozygotic twins with discordant physical activity.

Background & Aims: Ectopic fat in muscle and liver is linked to obesity and type 2 diabetes. Recently, pancreatic lipid accumulation has also been associated with β-cell dysfunction and reduced insulin production, leading to the development of type 2 diabetes. Physical exercise training has been shown to attenuate β-cell dysfunction in patients, but little is known about its effects on pancreatic and hepatic fat accumulation. In this study, we validated in-vivo proton magnetic resonance spectroscopy ((1)H MRS) in pancreatic fat measurement with biochemical measurements in a pig model. Thereafter, the effects of increased physical activity on the amounts of pancreatic and liver fat were studied in eight monozygotic twin pairs who have discordant physical activity and fitness.

Methods: Pancreatic fat content was studied in 15 pigs using (1)H MRS and/or biochemical analyses. In addition, liver and pancreatic fat were assessed using (1)H MRS in eight monozygotic male twin pairs with 18% mean difference in VO(2max) between the twin brothers.

Results: Twins with higher physical fitness had 23% less liver fat (1.3±1.3% vs. 2.1±2.6%, p=0.022) but no such difference was observed in the pancreatic fat (8.2±9.3% vs. 9.8±8.5%, respectively, p=0.3). Hepatic fat content was inversely associated with VO(2max). A positive association was found between pancreatic and liver fat contents (β=5.18, p=0.012). Pancreatic fat content was also associated with insulin sensitivity indexes and plasma adiponectin and glutamyltransferase concentrations.

Conclusions: Pancreatic fat content is associated with insulin resistance and hepatic fat content. An active lifestyle seems to beneficially influence hepatic fat metabolism.