Evidence for gut factor in K+ homeostasis.

We tested the hypothesis that K(+) intake is sensed by putative K(+) sensors in the splanchnic areas, and renal K(+) handling is regulated by this signal. K(+) was infused for 2 h into overnight-fasted rats via the jugular vein (systemic infusion), hepatic portal vein (intraportal infusion), or stomach (intragastric infusion) (n = 5 each), and plasma K(+) concentration ([K(+)]) and renal K(+) excretion were measured during the 2-h preinfusion, 2-h K(+) infusion, and 3-h washout periods. During systemic K(+) infusion, plasma [K(+)] increased by approximately 1.

Insulin regulation of skeletal muscle PDK4 mRNA expression is impaired in acute insulin-resistant states.

We previously showed that insulin has a profound effect to suppress pyruvate dehydrogenase kinase (PDK) 4 expression in rat skeletal muscle. In the present study, we examined whether insulin's effect on PDK4 expression is impaired in acute insulin-resistant states and, if so, whether this change is accompanied by decreased insulin's effects to stimulate Akt and forkhead box class O (FOXO) 1 phosphorylation. To induce insulin resistance, conscious overnight-fasted rats received a constant infusion of Intralipid or lactate for 5 h, while a control group received saline infusion.

Insulin suppresses PDK-4 expression in skeletal muscle independently of plasma FFA.

Starvation and experimental diabetes induce a stable increase in pyruvate dehydrogenase kinase (PDK) activity in skeletal muscle, which is largely due to a selective upregulation of PDK-4 expression. Increased free fatty acid (FFA) level has been suggested to be responsible for the upregulation. Because these metabolic states are also characterized by insulin deficiency, the present study was designed to examine whether insulin has a significant effect to regulate PDK mRNA expression in rat skeletal muscle.

Lactate induces insulin resistance in skeletal muscle by suppressing glycolysis and impairing insulin signaling.

Elevation of plasma lactate levels induces peripheral insulin resistance, but the underlying mechanisms are unclear. We examined whether lactate infusion in rats suppresses glycolysis preceding insulin resistance and whether lactate-induced insulin resistance is accompanied by altered insulin signaling and/or insulin-stimulated glucose transport in skeletal muscle. Hyperinsulinemic euglycemic clamps were conducted for 6 h in conscious, overnight-fasted rats with or without lactate infusion (120 micromol x kg(-1) x min(-1)) during the final 3.

Independent regulation of in vivo insulin action on glucose versus K(+) uptake by dietary fat and K(+) content.

Insulin stimulates both glucose and K(+) uptake, and high-fat feeding is known to decrease insulin-stimulated glucose uptake. The purpose of this study was to examine whether insulin's actions on glucose and K(+) uptake are similarly decreased by a high-fat diet. Wistar rats were fed a standard control (12.