Effects of ingested fructose and infused glucagon on endogenous glucose production in obese NIDDM patients, obese non-diabetic subjects, and healthy subjects

Abstract

SummaryIncreased endogenous glucose production (EGP) and gluconeogenesis contribute to the patho-genesis of hyperglycaemia in non-insulin-dependent diabetes mellitus (NIDDM). In healthy subjects, however, EGP remains constant during administration of gluconeogenic precursors. This study was performed in order to determine whether administration of fructose increases EGP in obese NIDDM patients and obese non-diabetic subjects. Eight young healthy lean subjects, eight middle-aged obese NIDDM patients and seven middle-aged obese non-diabetic subjects were studied during hourly ingestion of 13 C fructose (0.3 g · kg fat free mass -1 · h -1 ) for 3 h. Fructose failed to increase EGP (measured with 6,6 2 H glucose) in NIDDM (17.7 ± 1.9 µmol · kg fat free mass -1 · min -1 basal vs 15.9 ± 0.9 after fructose), in obese non-diabetic subjects (12.1 ± 0.5 basal vs 13.1 ± 0.5 after fructose) and in lean healthy subjects (13.3 ± 0.5 basal vs 13.8 ± 0.6 after fructose) although 13 C glucose synthesis contributed 73.2 % of EGP in lean subjects, 62.6 % in obese non-diabetic subjects, and 52.8 % in obese NIDDM patients. Since glucagon may play an important role in the development of hyperglycaemia in NIDDM, healthy subjects were also studied during 13 C fructose ingestion + hyperglucagonaemia (232 ± 9 ng/l) and during hyperglucagonaemia alone. EGP increased by 19.8 % with ingestion of fructose + glucagon (p < 0.05) but remained unchanged during administration of fructose or glucagon alone. The plasma 13 C glucose enrichment was identical after fructose ingestion both with and without glucagon, indicating that the contribution of fructose gluconeogenesis to the glucose 6-phosphate pool was identical in these two conditions. We concluded that during fructose administration: 1) gluconeogenesis is increased, but EGP remains constant in NIDDM, obese non-diabetic, and lean individuals; 2) in lean individuals, both an increased glucagonaemia and an enhanced supply of gluconeogenic precursors are required to increase EGP; this increase in EGP occurs without changes in the relative proportion of glucose 6-phosphate production from fructose and from other sources (i. e. glycogenolysis + gluconeogenesis from non-fructose precursors). [Diabetologia (1996) Abbreviations: EGP, Endogenous glucose production ; CHO, carbohydrate ; APE, atom percent excess ; GRd, glucose rate of disappearance ; FFM, fat-free mass.In healthy human subjects and in normal dogs, endogenous glucose production (EGP) has been shown not to rise when gluconeogenic substrates are infused and gluconeogenesis is increased [1][2][3][4][5]. This constancy of EGP was also observed during infusions of lactate [2] or fructose [5] when insulin and glucagon were maintained constant by infusions of somatostatin, insulin and glucagon, indicating autoregulation. The mechanisms responsible for this autoregulation of EGP may involve inhibition of gluconeogenesis from endogenous substrates [3] and/or of glucogenolysis [2] and stimulation of glycogen synthesis [5]. In non-insulin-depende...

Effects of roux‐en‐Y gastric bypass surgery on postprandial fructose metabolism

“…set at 0.2, G is the glucose concentration (mg/l), E is the 6,6-2 H 2 -glucose isotopic enrichment (mol% excess), and t is the time of collection (min) (16). Parameters were set assuming that kinetics for 13 C-glucose appearance in blood after ingestion of a 13 C-labeled glucose load apply to the ingestion of a 13 C-labeled fructose load as well (17).…”

Effect of dietary energy restriction on glucose production and substrate utilization in type 2 diabetes.

“…That reduction in EGP by 21% could occur by a starvation-induced glycogen depletion mechanism is unlikely a priori if glycogen provided only 12% of EGP at baseline in type 2 diabetes, as was concluded using the NMR method (7). A primary role for glycogenolysis as a modulating pathway over EGP in type 2 diabetes is consistent with the failure of either reducing gluconeogenesis substrate availability (with ethanol) (34) or increasing gluconeogenesis substrate availability (with fructose) (35) to alter EGP in diabetic subjects, as in healthy control subjects (33,36).…”

A new paradigm for treating obesity and diabetes mellitus

“…One crucial feature before using such a triagonist in humans would be to have a well-balanced glucagon activity. Indeed, glucagon is known as a counterregulatory hormone that exerts a potent hyperglycaemic effect by increasing hepatic glucose output through the stimulation of both glycogenolysis and gluconeogenesis 9 . Some experimental data suggested that glucagon suppression or inactivation may provide therapeutic advantages over insulin monotherapy 10 .…”