Increased Malonyl-CoA Levels in Muscle From Obese and Type 2 Diabetic Subjects Lead to Decreased Fatty Acid Oxidation and Increased Lipogenesis; Thiazolidinedione Treatment Reverses These Defects
Article Figures & Tables
Figures
- FIG. 1.
Malonyl-CoA (A) and phospho-ACC (B) levels, AMPK (C) and MCD (D) activities, and phospho-AMPK levels (E) in muscle from lean, obese (Ob), and type 2 diabetic subjects before and after hyperinsulinemic-euglycemic clamp. A group of type 2 patients were also treated with rosiglitazone (Rosi) for 3 months. At the end of the treatment period, muscle biopsies were taken before and after the clamp. Equal amounts of proteins were loaded for Western blotting, and the signals for phospho-ACC were normalized against total ACC after densitometric scan. A: *P < 0.03 vs. lean basal, †P < 0.05 vs. type 2 basal. B: *P < 0.01 vs. lean basal, **P < 0.05 vs. type 2 basal. C: *P < 0.05 vs. lean basal, **P < 0.02 vs. type 2 basal. D: *P < 0.05 vs. corresponding basal. E: *P < 0.01 vs. corresponding basal. □, basal; ▪, insulin. Ins, insulin; T 2D, type 2 diabetes.
- FIG. 2.
Intramyocellular triacylglycerol (A) and long-chain fatty acyl-coA (B) levels in human muscle. Source of tissues are same as in Fig. 1. A: *P < 0.05 vs. lean basal. B: *P < 0.01 vs. lean basal, †P < 0.05 vs. lean basal, #P < 0.03 vs. lean insulin treated, §P < 0.05 vs. type 2 basal, **P < 0.05 vs. type 2 basal. □, basal; ▪, insulin. Ob, obese.
- FIG. 3.
[1-14C]palmitate oxidation in tissue homogenates (A) and in isolated mitochondria (B) from muscle biopsies obtained from subjects as described in Fig. 1. A: *P < 0.02 vs. lean basal, †P < 0.05 vs. lean insulin treated, **P < 0.05 vs. type 2 basal, #P < 0.05 vs. type 2 insulin treated. B: *P < 0.01 vs. lean basal, **P < 0.02 vs. type 2 basal. □, basal; ▪, insulin. DPM, disintegrations per minute; Rosi, rosiglitazone.
- FIG. 4.
[1-14C]palmitate oxidation in isolated mitochondria in the presence or absence of malonyl-CoA. Mitochondria were isolated from muscle biopsies from subjects as described in Fig. 1. Mitochondria were preincubated with buffer or 25 μmol/l malonyl-CoA for 15 min before adding labeled palmitate. *P < 0.01 vs. lean basal, **P < 0.05 vs. lean insulin treated, †P < 0.03 vs. type 2 basal, and ‡P < 0.05 vs. type 2 insulin treated. □, basal; ▪, plus malonyl-CoA. DPM, disintegrations per minute; Rosi, rosiglitazone.
- FIG. 5.
Expression and insulin-stimulated translocation of fatty acid transporters in muscle membranes before and after treatment with rosiglitazone. The immunoblots representing expression of FATP4 and FAT/CD36 in muscle homogenates (A) and insulin-stimulated translocation of FATP4 and FAT/CD36 from microsomal compartment to plasma membrane (B) are shown. The signals were subjected to densitometric scan, and the areas under the curves (AU) were compared. Results are presented as histograms showing insulin-stimulated translocation of FAT/CD36 (C) and FATP4 (D) from microsome to plasma membrane. C: *P < 0.02 vs. lean basal plasma membrane, **P < 0.05 vs. lean basal microsome, †P < 0.03 vs. basal plasma membrane from type 2 diabetes plus rosiglitazone, and ‡P < 0.05 vs. basal microsome from type 2 diabetes plus rosiglitazone. D: *P < 0.01 vs. lean basal plasma membrane, **P < 0.05 vs. basal plasma membrane from type 2 diabetes plus rosiglitazone. Ins, insulin; Micro, microsomal compartment; PM, plasma membrane; Rosi, rosiglitazone.
Tables
- TABLE 1
Characteristics of study subjects
Parameters Nondiabetic Obese Type 2 diabetic Age (years) 47.25 ± 4.8 43.5 ± 4.0 53.08 ± 2.47 Weight (kg) 75.2 ± 5.4 96.7 ± 4.0 102.1 ± 7.6 BMI (kg/m2) 24.4 ± 1.2 33.3 ± 1.06* 36.93 ± 1.95* Fasting plasma glucose (mg/dl) 91.7 ± 2.16 92.0 ± 1.8 184.23 ± 16.3† Glucose infusion rate (mg · kg−1 · min−1) 9.9 ± 0.93 7.0 ± 0.37‡ 1.68 ± 0.42§ Plasma insulin (pmol/l) 66.7 ± 10 125.36 ± 26‖ 315 ± 78¶ Plasma free fatty acids (mmol/l) 346 ± 36 400 ± 30 750 ± 120# Plasma triacylglycerol (mg/dl) 88.75 ± 6.8 128.6 ± 21** 271 ± 75.1†† Data are means ± SE. A total of 8 nondiabetic (lean), 8 obese, and 13 type 2 diabetic subjects were involved in this study. All P values were determined by comparing with nondiabetic (lean) subjects.
- *
* P < 0.05,
- †
† P < 0.005,
- ‡
‡ P < 0.05,
- §
§ P < 0.002,
- ‖
‖ P < 0.02,
- ¶
¶ P < 0.02,
- #
# P < 0.02,
- **
** P = 0.05,
- ††
†† P < 0.05.
- TABLE 2
Clinical characteristics of type 2 subjects treated with rosiglitazone
Parameters Baseline After 3 months of treatment Age (years) 54.5 ± 2.37 — Weight (kg) 106.35 ± 9.3 108.38 ± 9.8 BMI (kg/m2) 36.7 ± 3.15 — Glucose disposal, Rd (mg · kg−1 · min−1) 3.54 ± 0.56 5.81 ± 1.0 Glucose infusion rate (mg · kg−1 · min−1) 1.15 ± 0.46 3.94 ± 1.05 Fasting plasma glucose (mg/dl) 162.5 ± 13.9 142.8 ± 13.6* Hepatic glucose output (mg · kg−1 · min−1) 2.39 ± 0.24 1.87 ± 0.16* Plasma cholesterol (mg/dl) 200.3 ± 22.85 207 ± 18.47 Plasma LDL cholesterol (mg/dl) 132.33 ± 15.74 139.67 ± 10.42 Plasma HDL cholesterol (mg/dl) 34.83 ± 2.56 32.67 ± 2.39 Plasma triacylglycerol (mg/dl) 165.3 ± 36.9 164.6 ± 40.5 HbA1c (%) 7.5 ± 0.4 7.2 ± 0.33 Data are means ± SE. Of the 13 type 2 diabetic patients, 6 were treated with rosiglitazone for 3 months, and clinical parameters were determined before and after treatment. All P values are based on comparison between numbers obtained before and after rosiglitazone treatment of type 2 diabetic subjects.
- *
* P < 0.03, pre- vs. posttreatment.
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