David Herzig

Aim To evaluate whether caffeine combined with a moderate amount of glucose reduces the risk for exercise‐related hypoglycaemia compared with glucose alone or control in adult people with type 1 diabetes using ultra‐long‐acting insulin degludec. Materials and Methods Sixteen participants conducted three aerobic exercise sessions (maximum 75 min) in a randomized, double‐blind, cross‐over design. Thirty minutes before exercise, participants ingested a drink containing either 250 mg of caffeine + 10 g of glucose + aspartame (CAF), 10 g of glucose + aspartame (GLU), or aspartame alone (ASP). The primary outcome was time to hypoglycaemia. Results There was a significant effect of the condition on time to hypoglycaemia (χ 2 = 7.674, p = .0216). Pairwise comparisons revealed an 85.7% risk reduction of hypoglycaemia for CAF compared with ASP ( p = .044). No difference was observed between GLU and ASP ( p = .104) or between CAF and GLU ( p = .77). While CAF increased glucose levels during exercise compared with GLU and ASP (8.3 ± 1.9 mmol/L vs. 7.7 ± 2.2 mmol/L vs. 5.8 ± 1.4 mmol/L; p < .001), peak plasma glucose levels during exercise did not differ between CAF and GLU (9.3 ± 1.4 mmol/L and 9.1 ± 1.6 mmol/L, p = .80), but were higher than in ASP (6.6 ± 1.1 mmol/L; p < .001). The difference in glucose levels between CAF and GLU was largest during the last 15 min of exercise ( p = .002). Compared with GLU, CAF lowered perceived exertion ( p = .023). Conclusions Pre‐exercise caffeine ingestion combined with a low dose of glucose reduced exercise‐related hypoglycaemia compared with control while avoiding hyperglycaemia.

The liver plays a central role in metabolic homeostasis, as exemplified by a variety of clinical disorders with hepatic and systemic metabolic disarrays. Of particular interest are the complex interactions between lipid and carbohydrate metabolism in highly prevalent conditions such as obesity, diabetes, and fatty liver disease. Limited accessibility and the need for invasive procedures challenge direct investigations in humans. Hence, noninvasive dynamic evaluations of glycolytic flux and steady‐state assessments of lipid levels and composition are crucial for basic understanding and may open new avenues toward novel therapeutic targets. Here, three different MR spectroscopy (MRS) techniques that have been combined in a single interleaved examination in a 7T MR scanner are evaluated. 1 H‐MRS and 13 C‐MRS probe endogenous metabolites, while deuterium metabolic imaging (DMI) relies on administration of deuterated tracers, currently 2 H‐labelled glucose, to map the spatial and temporal evolution of their metabolic fate. All three techniques have been optimized for a robust single‐session clinical investigation and applied in a preliminary study of healthy subjects. The use of a triple‐channel 1 H/ 2 H/ 13 C RF coil enables interleaved examinations with no need for repositioning. Short‐echo‐time STEAM spectroscopy provides well resolved spectra to quantify lipid content and composition. The relative benefits of using water saturation versus metabolite cycling and types of respiratory synchronization were evaluated. 2 H‐MR spectroscopic imaging allowed for registration of time‐ and space‐resolved glucose levels following oral ingestion of 2 H‐glucose, while natural abundance 13 C‐MRS of glycogen provides a dynamic measure of hepatic glucose storage. For DMI and 13 C‐MRS, the measurement precision of the method was estimated to be about 0.2 and about 16 mM, respectively, for 5 min scanning periods. Excellent results were shown for the determination of dynamic uptake of glucose with DMI and lipid profiles with 1 H‐MRS, while the determination of changes in glycogen levels by 13 C‐MRS is also feasible but somewhat more limited by signal‐to‐noise ratio.