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Postabsorptive and insulin-stimulated energy and protein metabolism in patients with myotonic dystrophy type 1^1,2,3

¹ From the Internal Medicine Section of Nutrition/Metabolism (GP, SB, RL, FC, GL, and LL), the Division of Nuclear Medicine (PS), the Division of Neurology (MC), the Division of Diagnostic Radiology (PS, FdC, and AdM), and the Unit of Clinical Spectroscopy (GP, PS, FdC, AdM, and LL), Università Vita e Salute San Raffaele, Istituto Scientifico H San Raffaele, Milan, Italy, and the International Center for the Assessment of Nutritional Status (AB) and the Faculty of Exercise Sciences (LL), Università degli Studi di Milano, Milan, Italy

Background: Exaggerated insulin resistance was described as the major metabolic abnormality in myotonic dystrophy type 1 (DM1). We reported recently that the severity of the impairment in insulin-stimulated glucose metabolism in these patients was overestimated.

Objective: The aim was to dissect out insulin action with respect to whole-body energy homeostasis and glucose, protein, and lipid metabolism in patients with DM1 to assess the relevance of insulin resistance to the heterogeneous clinical manifestations of this syndrome.

Design: Ten nondiabetic patients with DM1 and 10 matched healthy control subjects were studied by means of 1) dual-energy X-ray absorptiometry; 2) a euglycemic-hyperinsulinemic clamp (40 mU · m^–2 · min^–1) combined with a primed, continuous infusion of [6,6-d₂]glucose and [1-¹³C]leucine; 3) indirect calorimetry; and 4) localized ¹H magnetic resonance spectroscopy of the calf muscles.

Results: Patients with DM1 had less lean body mass, greater fat mass, and greater intramyocellular lipid contents than did healthy control subjects. Energy expenditure and glucose and lipid metabolism did not differ significantly between the groups. In contrast, markers of proteolysis were higher in DM1 patients in the postabsorptive and insulin-stimulated conditions and were associated with lower plasma concentrations of insulin-like growth factor 1 (P < 0.03) and higher plasma concentrations of tumor necrosis factor receptor 2 (P = 0.04).

Conclusions: Despite greater body fat and intramyocellular lipid contents in patients with DM1, insulin sensitivity was not significantly different between patients and control subjects. In contrast, the loss of lean body mass in patients with DM1 was associated with abnormal postabsorptive and insulin-stimulated regulation of protein breakdown. Lower plasma insulin-like growth factor 1 concentrations and higher tumor necrosis factor system activity might be involved in the muscle wasting of DM1.

Key Words: Insulin sensitivity • intramyocellular lipid content • leucine metabolism • fatty acid metabolism • indirect calorimetry • ¹H magnetic resonance spectroscopy

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				G. Lattuada, L. P. Sereni, D. Ruggieri, A. Scollo, S. Benedini, F. Ragogna, F. Costantino, A. Battezzati, L. Luzi, and G. Perseghin Postabsorptive and Insulin-Stimulated Energy Homeostasis and Leucine Turnover in Offspring of Type 2 Diabetic Patients Diabetes Care, November 1, 2004; 27(11): 2716 - 2722. [Abstract] [Full Text] [PDF]