Inhibition of Fructose 1,6-Bisphosphatase Reduces Excessive Endogenous Glucose Production and Attenuates Hyperglycemia in Zucker Diabetic Fatty Rats
Article Figures & Tables
Figures
- FIG. 1.
Structures of MB06322 and MB05032. MB06322 is an oral prodrug of MB05032, a potent FBPase inhibitor (IC50 [half-maximal inhibitory concentration] 16 nmol/l) (26) that binds to the allosteric AMP-binding site of the enzyme. MB06322 is converted to MB05032 in vivo via the sequential actions of an esterase and phosphoramidase.
- FIG. 2.
Effect of acute MB06322 administration (300 mg/kg) on endogenous glucose production (EGP) rates (A), the fractional contribution of gluconeogenesis and glycogenolysis to endogenous glucose production (B), and gluconeogenesis and glycogenolysis rates (C) in fasting conscious ∼10-week-old male ZDF rats. Endogenous glucose production was determined by standard tracer methodology, whereas the fractional contribution of gluconeogenesis and glycogenolysis to endogenous glucose production was determined by the deuterated water method, as described in research design and methods. Statistical analysis was not applied to the gluconeogenesis and glycogenolysis rates because they are the products of parameters (endogenous glucose production and fractional contributions of gluconeogenesis and glycogenolysis at 1:00 p.m.) measured in two different, but carefully matched, sets of animals (n = 6 per group). *P < 0.05 compared with vehicle (Student’s t test).
- FIG. 3.
Effects of MB06322 prevention and intervention therapy in male ZDF rats. A: Blood glucose (nonfasted). B: Plasma insulin (nonfasted). C: Blood glucose levels during an oral glucose tolerance test administered after 5 weeks of treatment in the prevention study. To reflect metabolic changes independent of acute gluconeogenesis inhibition, the food/drug admixture was withdrawn for 6 h before administration of a 2-g/kg oral glucose load. Baseline blood glucose levels were 540 ± 19 and 201 ± 49 mg/dl for control and drug-treated animals, respectively. D: Insulin levels during the oral glucose tolerance test in the prevention study. Drug was administered as a food admixture (0.4%, wt/wt) to 6-week-old (prevention) and 10-week-old (intervention) rats as described in research design and methods. Based on food intake, the average dose of MB06322 administered was 400 mg · kg−1 · day−1, which is well in excess of the 30-mg/kg dose required for a profound, acute glucose-lowering effect in this model (28). When drug therapy was withdrawn at 12 weeks of age, blood glucose gradually rebounded to levels approximating those of the control animals in both treated groups (not shown), n = 8 per group. *P < 0.05 compared with controls (ANOVA).
- FIG. 4.
MB06322 treatment of high-fat diet–fed female ZDF rats. A: Blood glucose (nonfasted). B: Plasma insulin (nonfasted). Rats were fed a high-fat diet (48% kcal fat) for 30 days before administration of MB06322 as a high-fat chow admixture, as described in research design and methods. The 100- and 300-mg/kg doses are 3- and 10-fold multiples, respectively, of the minimum dose that elicits 30% blood glucose lowering in this model (50), n = 8 per group. *P < 0.05 compared with controls (repeated-measures ANOVA).
Tables
- TABLE 1
Physiological and metabolic parameters in control and MB06322-treated pre-diabetic male ZDF rats (nonfasted)*
Parameter Control MB06322 (0.4%) prevention MB06322 (0.4%) intervention Age 6 weeks Age 10 weeks Age 12 weeks Age 6 weeks Age 10 weeks Age 12 weeks Age 10 weeks Age 12 weeks Length of treatment (weeks) 0 4 6 0 4 6 0 2 Lactate (mmol/l)† 1.85 ± 0.11 1.9 ± 0.09 1.73 ± 0.05 1.76 ± 0.09 1.89 ± 0.21 2.66 ± 0.62 1.83 ± 0.15 3.11 ± 0.27‡ NEFA (mmol/l) 0.9 ± 0.04 2.1 ± 0.1 4.9 ± 0.2 1.0 ± 0.05 2.8 ± 0.2‡ 6.1 ± 0.22‡ 1.8 ± 0.2 5.23 ± 3 Triglycerides (mg/dl) 191 ± 11 598 ± 45 609 ± 53 210 ± 17 713 ± 57 1,016 ± 97‡ 640 ± 60 945 ± 88‡ Cholesterol (mg/dl) 72 ± 3 137 ± 4 144 ± 5 83 ± 3‡ 152.±8 175 ± 20 153 ± 6 236 ± 8‡ β-OH-butyrate (μmol/l) — — 223 ± 14 — — 158 ± 17‡ — 182 ± 12‡ Water intake (ml/day) 28 ± 3 111 ± 5 144 ± 4 30 ± 1 44 ± 5‡ 35 ± 4‡ 116 ± 2 42 ± 2‡ Food intake (g/day) 28 ± 1 33 ± 0 36 ± 0 27 ± 0 33 ± 1 36 ± 2 32 ± 0 33 ± 0‡ Body weight (g) 184 ± 3 337 ± 5 365 ± 6 191 ± 2 361 ± 5‡ 423 ± 11‡ 335 ± 8 358 ± 8 -
Data are means ± SE.
- *
* Weekly measurements were made. Parameters measured after 2 or 4 and 6 weeks of treatment are shown to highlight metabolic changes that occurred during these time periods.
- †
† The lactate elevations observed in the prevention and intervention groups were resolved within 3 days after the cessation of drug treatment;
- ‡
‡ P < 0.05 vs. control, Student’s t test.
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- TABLE 2
Physiological and metabolic parameters in control and MB06322-treated pre-diabetic male ZDF rats (nonfasted): metabolic cage measurements
Parameter Control MB06322 (0.4%) prevention MB06322 (0.4%) intervention 0.5 weeks of treatment 2.5 weeks of treatment 4.5 weeks of treatment 0.5 weeks of treatment 2.5 weeks of treatment 4.5 weeks of treatment 0 weeks of treatment 0.5 weeks of treatment Age (weeks) 6.5 8.5 10.5 6.5 8.5 10.5 10 10.5 Water intake (ml/day) 27 ± 2.3 79 ± 8 151 ± 5 24 ± 2 37 ± 3* 44 ± 7* — 79 ± 4* Urine output (ml/day) 15 ± 1 62 ± 7 121 ± 5 14 ± 1 21 ± 2* 29 ± 1* — 55 ± 3* Glucose excretion (g/day) 0.38 ± 0.18 7.87 ± 1.67 16.74 ± 1.97 0.026 ± 0.07 0.99 ± 0.21* 3.28 ± 1.59* — 5.25 ± 0.67* -
Data are means ± SE.
- *
* P < 0.05 vs. control for corresponding timepoint, unpaired Student’s t test.
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- TABLE 3
Physiological and metabolic parameters in control and MB06322-treated high-fat diet–fed female ZDF rats (nonfasted)
Parameter Control MB06322 (100 mg · kg−1 · day−1) MB06322 (300 mg · kg−1 · day−1) 0 days of treatment 14 days of treatment 0 days of treatment 14 days of treatment 0 days of treatment 14 days of treatment Insulin (ng/ml) 29.3 ± 4.7 17.2 ± 3.4 28.6 ± 5 14.2 ± 1 26.9 ± 5.3 12.9 ± 1.4 Glucagon (pg/ml) — 122 ± 6 — 114 ± 6 — 108 ± 8 Lactate (mmol/l) 1.22 ± 0.18 1.94 ± 0.46 1.12 ± 0.08 1.63 ± 0.51 1.58 ± 0.16 1.55 ± 0.26 NEFA (mmol/l) — 1.2 ± 0.3 — 1.1 ± 0.1 — 1.2 ± 0.1 Triglycerides (mg/dl) 1,291 ± 120 1,706 ± 229 1,110 ± 103 1,145 ± 164 1,094 ± 154 1,154 ± 60 Cholesterol (mg/dl) — 133 ± 8 — 120 ± 5 — 158 ± 4 β-Hydroxybutyrate (μmol/l) — 133 ± 13 — 132 ± 16 — 117 ± 12 Liver triglycerides (mg/g) — 15.3 ± 2.5 — 13 ± 3 — 12 ± 1 Liver glycogen (μmol/g) — 276 ± 11 — 244 ± 13 — 222 ± 13* Alkaline phosphatase (IU/ml) — 196 ± 28 — 110 ± 8* — 118 ± 14* Water intake (ml/day) 27 ± 5 31 ± 6 29 ± 5 15 ± 2 30 ± 6 16 ± 1 Food intake (g/day) 16 ± 1 17 ± 1 15 ± 1 15 ± 1 15 ± 1 13 ± 2 Body weight (g) 339 ± 5 388 ± 7 326 ± 4 370 ± 4 323 ± 7 360 ± 9 -
Data are means ± SE.
- *
* P < 0.05 vs. control, ANOVA with Dunnett’s post hoc test.
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