Catecholamine regulation of local lactate production in vivo in skeletal muscle and adipose tissue: role of -adrenoreceptor subtypes.

Context: The regulation of lactate production in skeletal muscle (SM) and adipose tissue (AT) is not fully elucidated.

Objective: Our objective was to investigate the catecholamine-mediated regulation of lactate production and blood flow in SM and AT in healthy, normal-weight subjects by using microdialysis.

Methods: First, lactate levels in SM and AT were measured during an iv norepinephrine infusion (n = 11).

Human skeletal muscle lipolysis is more responsive to epinephrine than to norepinephrine stimulation in vivo.

Context: Triglyceride (TG) deposits in skeletal muscle (SM) are an important energy reservoir, and increased im TG content is associated with muscle insulin resistance.

Objective: The objective of the study was to investigate the effect of endogenous catecholamines on TG lipolysis in human SM in vivo. Adipose tissue (AT) was studied for comparison.

Marked reutilization of free fatty acids during activated lipolysis in human skeletal muscle.

Release of glycerol and free fatty acids (FFA) was investigated in human skeletal muscle strips. In the basal state, glycerol and FFA were released at almost equimolar rates (0.3 nmol/ng tissue.

Combined hyperinsulinemia and hyperglycemia, but not hyperinsulinemia alone, suppress human skeletal muscle lipolytic activity in vivo.

Effects of circulating insulin and glucose concentrations on skeletal muscle and adipose tissue lipolytic activity were investigated in 10 type 1 diabetes patients with no endogenous insulin secretion. Microdialysis measurements of interstitial glycerol and determination of fractional glycerol release were carried out during standardized combinations of relative hypoinsulinemia/moderate hyperglycemia (11 mmol/liter), hyperinsulinemia/ normoglycemia (5 mmol/liter), and hyperinsulinemia/moderate hyperglycemia, respectively. Local tissue blood flow rates were measured with the (133)Xe clearance technique.

Defective activation of skeletal muscle and adipose tissue lipolysis in type 1 diabetes mellitus during hypoglycemia.

The increased risk of hypoglycemia during intensified treatment of type 1 diabetes mellitus (T1DM) patients, who have a deficient glucagon secretory response, is largely attributed to the development of suppressed adrenomedullary responses. A consequence of this impairment of catecholamine secretion might be reduced lipolysis in major target tissues (muscle and adipose) and, in turn, increased glucose metabolism. To test this hypothesis, we used microdialysis to monitor glycerol (index of lipolysis) in the extracellular fluid of skeletal muscle and adipose tissue and assessed whole-body glucose use by measuring [6,6-(2)H(2)]glucose enrichment in plasma in seven intensively treated T1DM patients and eight nondiabetic subjects who received a 3-h insulin infusion (0.

Marked heterogeneity of human skeletal muscle lipolysis at rest.

In this study, variations in lipolysis among different muscle groups were examined by measuring local net glycerol release in vivo in healthy, normal-weight subjects (n = 11) during rested, postabsorptive conditions. Microdialysis of the gastrocnemius, deltoid, and vastus lateralis muscle regions revealed that extracellular glycerol concentrations of these three muscle regions were 84.7 +/- 6.

Assessment of skeletal muscle triglyceride content by (1)H nuclear magnetic resonance spectroscopy in lean and obese adolescents: relationships to insulin sensitivity, total body fat, and central adiposity.

The metabolism and composition of skeletal muscle tissue is of special interest because it is a primary site of insulin action and plays a key role in the pathogenesis of insulin resistance. Intramyocellular (IMCL) triglyceride stores are an accessible form of energy that may decrease skeletal muscle glucose utilization, thereby contributing to impaired glucose metabolism. Because of the invasive nature of muscle biopsies, there is limited, if any, information about intramuscular lipid stores in children.