Local NOS inhibition impairs vascular and metabolic actions of insulin in rat hindleg muscle in vivo

Abstract

Bradley EA, Richards SM, Keske MA, Rattigan S. Local NOS inhibition impairs vascular and metabolic actions of insulin in rat hindleg muscle in vivo. Am J Physiol Endocrinol Metab 305: E745-E750, 2013. First published July 30, 2013 doi:10.1152/ajpendo.00289.2013.-Insulin stimulates microvascular recruitment in skeletal muscle, and this vascular action augments muscle glucose disposal by ϳ40%. The aim of the current study was to determine the contribution of local nitric oxide synthase (NOS) to the vascular actions of insulin in muscle. Hooded Wistar rats were infused with the NOS inhibitor N -nitro-L-arginine methylester (L-NAME, 10 M) retrogradely via the epigastric artery in one leg during a systemic hyperinsulinemiceuglycemic clamp (3 mU·min Ϫ1 ·kg Ϫ1 ϫ 60 min) or saline infusion. Femoral artery blood flow, microvascular blood flow (assessed from 1-methylxanthine metabolism), and muscle glucose uptake (2-deoxyglucose uptake) were measured in both legs. Local L-NAME infusion did not have any systemic actions on blood pressure or heart rate. Local L-NAME blocked insulin-stimulated changes in femoral artery blood flow (84%, P Ͻ 0.05) and microvascular recruitment (98%, P Ͻ 0.05), and partially blocked insulin-mediated glucose uptake in muscle (reduced by 34%, P Ͻ 0.05). L-NAME alone did not have any metabolic effects in the hindleg. We conclude that insulinmediated microvascular recruitment is dependent on local activation of NOS in muscle and that this action is important for insulin's metabolic actions. muscle blood flow; microvascular blood flow; hyperinsulinemiceuglycemic clamp; nitric oxide; nitric oxide synthase INSULIN STIMULATES TOTAL LIMB blood flow and recruits flow to the microvasculature in skeletal muscle (21,31,32,34). These vascular actions occur in both humans (6, 33) and experimental animals (21,31,32,34). We (4), and others (1, 2), have proposed that insulin-mediated vascular responses facilitate insulin and glucose delivery to the myocyte and thereby enhance the rate of glucose disposal. Insulin-mediated increases in skeletal muscle blood flow and microvascular responses are blunted in insulinresistant rats (26, 36) and humans (6, 13), suggesting that reduced muscle perfusion may contribute to the insulin resistance. Recently, we demonstrated that insulin resistance induced by increased dietary fat can originate from impaired microvascular insulin responses and occur before the development of myocyte insulin resistance (18). Therefore, it is important to understand the mechanism by which insulin stimulates microvascular recruitment under healthy circumstances to identify the basis of vascularderived insulin resistance.Studies by Steinberg et al. (27) and Scherrer et al. (23) have demonstrated that local infusion of a nitric oxide synthase (NOS) inhibitor completely abolishes insulin-in-

Blueberry Tea Enhances Insulin Sensitivity by Augmenting Insulin-Mediated Metabolic and Microvascular Responses in Skeletal Muscle of High Fat Fed Rats

“…We have shown that acute defects in insulin-mediated microvascular recruitment can contribute to the development of muscle insulin resistance in vivo. Infusion of α-methyl serotonin [26], endothelin-1 [27], L-N G -Nitroarginine methyl ester [7,29,37], TNFα [38], Intralipid® plus heparin [39] and glucosamine [40] in healthy animals attenuate insulin-mediated microvascular recruitment and insulin-mediated muscle glucose uptake. In addition, chronic models of insulin resistance including the high fat-fed rat (36% fat wt/ wt) [3], and obese Zucker rat [41] display marked attenuation in insulin-mediated microvascular recruitment and muscle glucose uptake.…”

Insulin Resistance and Skeletal Muscle Vasculature: Significance, Assessment and Therapeutic Modulators

“…Furthermore, the concentrations of insulin required to cause an increased microvascular blood flow are lower than those required to increase whole-limb blood flow [26]. The role of bioavailable NO in skeletal muscle glucose uptake has been further clarified [53]. Recently, an investigative group has infused an eNOS inhibitor in the hind leg of anesthetized rats fed a regular diet [53].…”

“…The role of bioavailable NO in skeletal muscle glucose uptake has been further clarified [53]. Recently, an investigative group has infused an eNOS inhibitor in the hind leg of anesthetized rats fed a regular diet [53]. No changes were reported in blood pressure or heart rate, but eNOS inhibition significantly blunted the insulin-stimulated increase of ultrasound-assessed femoral blood flow [53].…”

“…Recently, an investigative group has infused an eNOS inhibitor in the hind leg of anesthetized rats fed a regular diet [53]. No changes were reported in blood pressure or heart rate, but eNOS inhibition significantly blunted the insulin-stimulated increase of ultrasound-assessed femoral blood flow [53]. In parallel, insulin-stimulated microvascular recruitment and glucose uptake were completely abolished [53].…”

Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients

“…However, aging and insulin resistance are associated with reduced skeletal muscle capillary density, impaired endothelial function, and reduced nitric oxide (NO) availability (14,20,32,39,40). As such, age-related impairments in vascular function due to an impaired NO-mediated vasodilatory response and decreased muscle tissue perfusion may diminish feeding-mediated increases in muscle protein synthesis and, thus, contribute to the anabolic resistance of aging (7,24).It has been reported that dietary nitrate (NO 3 Ϫ ) supplementation, via sequential reduction of NO 3 Ϫ to nitrite (NO 2 Ϫ ) and NO, can stimulate NO synthesis and increase NO bioavailability (55). Moreover, it has been suggested that NO has a role in promoting insulin delivery to skeletal muscle tissue and increasing insulin-stimulated muscle perfusion and capillary action (22, 51).…”