Diets high in fat and fructose (HFFD) disrupt glucose metabolism. The aim of this study was to determine if HFFD impairs hepatic glucose effectiveness (i.e., the ability of glucose per se to stimulate net hepatic glucose uptake [NHGU] and/or to suppress glucose production [Ra]). In overnight fasted dogs fed either a chow diet or HFFD for 1 month, somatostatin, 3-3H-glucose, and basal hepatic portal vein infusions of insulin and glucagon were given. After a basal sampling period, these infusions continued for 4h while glucose was infused to create a 3-fold rise in plasma glucose. Since hepatic glucose uptake is also stimulated by a negative arterial to portal vein glucose gradient, such as occurs with glucose ingestion, glucose was either all infused into a peripheral vein (Chow-PeG, n=6; HFFD-PeG, n=6), or a portion was also given into the portal vein (4 mg/kg/min; Chow-PoG, n=5; HFFD-PoG, n=5). There were no differences in plasma insulin, glucagon, arterial glucose, or hepatic glucose load between groups. In response to hyperglycemia, the liver switched from making (basal period) to storing (last h) glucose in the chow fed groups (1.1±0.1 to -2.0±0.5* mg/kg/min in Chow-PeG, and 1.3±0.1 to -3.0±0.9* in Chow-PoG; a negative rate indicates uptake). Conversely, HFFD markedly reduced liver glucose effectiveness. In fact, with HFFD the liver did not take up glucose in response to hyperglycemia whether the portal signal was absent (1.4±0.1 to 1.0±0.3 in HFFD-PeG) or present (1.6±0.3 to 0.0±0.3* in HFFD-PoG). Thus, in the Chow vs. HFFD groups, the impact of hyperglycemia on overall net hepatic glucose balance was 3.1±0.5 vs. 0.4±0.4* (13% of normal) in the absence of portal glucose delivery and 4.3±0.9 vs. 1.6±0.5* (37% of normal) in its presence. Hyperglycemia suppressed Ra by 75±12 vs. 22±6%* (last h) in Chow vs. HFFD-PeG, respectively, and by 81±14 vs. 34±7%* in Chow vs. HFFD-PoG.
In summary, HFFD induced a severe impairment in hepatic glucose effectiveness but did not affect the liver’s response to the portal glucose signal. (*P<0.05).
D.S. Edgerton: None. G. Kraft: None. B. Farmer: None. M. Scott: None. M.S. Smith: None. A.D. Cherrington: Advisory Panel; Self; Biocon, Fractyl Laboratories, Inc., Metavention, Sekkei Bio, Sensulin, LLC., vTv Therapeutics, Zafgen, Inc. Consultant; Self; Thetis Pharmaceuticals LLC. Research Support; Self; Diasome Pharmaceuticals, Inc. Other Relationship; Self; Abvance Therapeutics, Novo Nordisk Inc.
National Institutes of Health (R01DK18243)