1600-P: Duration of Morning Hyperinsulinemia Is Key to the Enhancement of Hepatic Glucose Uptake Later in the Day

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The second meal phenomenon, which occurs in normal and diabetic individuals, refers to the improvement in glucose tolerance seen following a second identical meal. We previously showed that 4h of morning (AM) hyperinsulinemia, but not hyperglycemia, enhanced hepatic glucose uptake (HGU) and glycogen storage during a PM hyperinsulinemic hyperglycemic clamp (HIHG) later that day. Our aim was to determine if the duration of morning hyperinsulinemia is important for the PM response to a HIHG clamp. To determine this, we administered the same amount of insulin over 2h in the first half of the morning (Ins2h-A), over 2h in the 2nd half of the morning (Ins2h-B), or over the entire 4h (Ins4h) of the morning. We then assessed the impact of the AM insulin duration on HGU during a PM HIHG clamp in conscious dogs. The dogs underwent an AM hyperinsulinemic euglycemic clamp from 0-120 min, 120-240 min, or 0-240 min (Ins2h-A, Ins2h-B, or Ins4h; n=6/group). The insulin infusion rates used in the Ins4h were selected to mimic the rise in endogenous insulin secretion previously observed during a 4h AM duodenal glucose infusion (2.1 mU/kg/min (0-30 min), 2.4 mU/kg/min (30-60 min), and 1.5 mU/kg/min (60-240 min)). These rates were doubled in both 2h groups to match the total amount of insulin being infused in the 4h AM clamp. In the PM, all groups had 4x basal insulin, 2x basal glycemia, and portal glucose infusion to simulate a 2nd meal. During the 4h PM clamp, there were no significant differences between the two 2h groups. However, there was a marked effect on the mean HGU in the Ins4h group compared to the Ins2h-A and Ins2h-B groups (HGU of 6.3±0.9 vs 3.8±0.3 and 4.4±0.4 mg/kg/min; AUC of 1393±199 vs 822±68 and 971±93 mg/kg/4hr, P<0.05), respectively, despite matched hepatic glucose loads. The longer duration (Ins4h) of AM hyperinsulinemia allowed for a 41% and 66% greater uptake of glucose in the PM clamp (vs Ins2hA + B). Thus, the duration of AM hyperinsulinemia is an important determinant of hepatic metabolism later in the day. Disclosure H.L.Waterman: None. M.S.Smith: None. B.Farmer: None. G.Kraft: None. M.Scott: None. D.S.Edgerton: None. A.D.Cherrington: Advisory Panel; Metavention, vTv Therapeutics, Diakard, Sekkei Bio, Sensulin Labs, LLC, Other Relationship; Fractyl Health, Inc., Novo Nordisk, Abvance Therapeutics, Research Support; Cellular Longevity, Inc, dba Loyal, Senda Biosciences. M.C.Moore: None. Funding National Institutes of Health (5T32DK007563-34, 5R01DK131082-02)