Fig. 5.

Upper small intestinal infusion of casein lowers glucose production in models of early-onset insulin resistance and obesity. Rats were fed a 3-day high-fat diet (HFD) and a pancreatic (basal insulin) euglycemic clamp was performed in rats as outlined in a. Rates of glucose infusion (b) and glucose production (GP, c) were determined in HFD rats that received an upper small intestinal (S.I.) infusion of saline (n = 7) or casein (n = 6). Rats were fed a regular chow (RC) or HFD for 28 days and a pancreatic (basal insulin) euglycemic clamp performed as outlined in (d). Cumulative food intake was monitored over the 28-day protocol (e). Body weight (f), fat mass (g), and lean mass (h) were measured at baseline (day 0) and at the end of the 28-day period. Rates of glucose infusion (i) and glucose production (j) were assessed following an upper S.I. infusion of saline (n = 5–6) or casein (n = 5–8). Values are presented as mean ± s.e.m., where basal and clamp represent the average GP of t = 60–90 or t = 190–200, respectively, and asterisk (*) represents p < 0.05 compared to respective saline control (b, c, i, j) or regular chow-fed rats (e–g). Statistical significance was determined using an unpaired, two-tailed t-test (two groups) or ANOVA with Tukey post-hoc test (3+ groups)