Title of project

The GALAXY-2 project: Galactose – a glucose-stabilizing fuel for skeletal muscle during exercise in individuals with type 1 diabetes

Abstract

Individuals with type 1 diabetes (T1D) experience significant challenges with glucose regulation in relation to exercise, with the risk of hypoglycemia. To prevent this, it is necessary to ingest carbohydrates which an lead to significant plasma glucose fluctuations. Galactose, an alternative carbohydrate, has demonstrated potential in providing a steadier glycemic response during exercise. However, to what extent galactose can be absorbed and directly utilization by human skeletal muscle remain unclear. Preliminary findings from our current study, where galactose was administered intravenously during exercise, reveal that galactose can be directly taken up by human skeletal muscle. This challenges the conventional understanding that galactose must first be converted to glucose in the liver before utilization. The primary objective of this project is to investigate whether exercise enhances the uptake of galactose in skeletal muscle following oral administration, both in healthy individuals and those with T1D. Our hypothesis is that exercise promotes galactose uptake independently of an increase in insulin secretion, leading to similar uptake levels in both healthy individuals and those with T1D. Additionally, we will explore whether co-ingestion of galactose with glucose reduces skeletal muscle uptake due to increased hepatic clearance. We will study this in a randomized crossover trial, involving eight healthy participants and eight participants with T1D. Each participant will undergo two study days performing a one-legged exercise, followed by ingesting either galactose alone or in combination with glucose. Whole-body galactose uptake will be assessed using 18F-FDGal positron emission tomography scans, focusing primarily on skeletal muscle uptake, with secondary outcomes including hepatic, cardiac, and cerebral uptake. The results of this study will provide critical insights into galactose metabolism and its potential role in managing exerciseinduced glycemic fluctuations, particularly in individuals with T1D. These findings may inform the development of new dietary strategies aimed at reducing hypoglycemia risk without the drawbacks associated with other carbohydrate sources.