Vasopressin is a major vasoconstrictor involved in hindlimb vascular responses to stimulation of adenosine A(1) receptors in the nucleus of the solitary tract

Sodium-glucose co-transporter 2 inhibitor use in patients with diabetes mellitus undergoing endovascular therapy for symptomatic peripheral artery disease

BACKGROUND

This study aimed to reveal the prevalence of sodium-glucose co-transporter 2 (SGLT2) inhibitor treatment and its association with restenosis risk in patients with diabetes mellitus undergoing endovascular therapy for symptomatic peripheral artery disease.

METHODS

We used the database of a multicenter prospective study registering patients with symptomatic peripheral artery disease undergoing femoropopliteal drug-coated balloon treatment in Japan. The current analysis included 1058 patients with diabetes mellitus free from end-stage renal disease. The association of clinical characteristics with SGLT2 inhibitor use was investigated using the logistic regression model. The propensity score matching was adopted to compare the primary patency, i.e., freedom from restenosis, after endovascular therapy between patients treated with and without a SGLT2 inhibitor.

RESULTS

The proportion of SGLT2 inhibitor treatment at revascularization was 14.8% (95% confidence interval, 12.8-17.1%). Younger age, increased body mass index, and increased hemoglobin A1c levels were independently associated with SGLT2 inhibitor use (all P < 0.05). The proportion of SGLT2 inhibitor reached 38.2% (95% confidence interval, 25.4-52.3%) in patients with the three associated factors. The propensity score-matching analysis demonstrated that primary patency was not different between patients treated with a SGLT2 inhibitor and those without it (72.0% [95% confidence interval, 64.1-80.9%] versus 67.8% [62.7-73.3%] at 2 years; P = 0.45).

CONCLUSIONS

SGLT2 inhibitors were not rarely used in patients with diabetes mellitus who underwent femoropopliteal endovascular therapy using a drug coated balloon for symptomatic peripheral artery disease in real-world settings. SGLT2 inhibitor treatment was not associated with an increased risk of restenosis.

V1a and V1b vasopressin receptors within the paraventricular nucleus contribute to hypertension in male rats exposed to chronic mild unpredictable stress

Depression is an independent nontraditional risk factor for cardiovascular disease and mortality. The chronic unpredictable mild stress (CMS) rat model is a validated model of depression. Within the paraventricular nucleus (PVN), vasopressin (VP) via V1aR and V1bR have been implicated in stress and neurocardiovascular dysregulation. We hypothesized that in conscious, unrestrained CMS rats versus control, unstressed rats, PVN VP results in elevated arterial pressure (MAP), heart rate, and renal sympathetic nerve activity (RSNA) via activation of V1aR and/or V1bR. Male rats underwent 4 wk of CMS or control conditions. They were then equipped with hemodynamic telemetry transmitters, PVN cannula, and left renal nerve electrode. V1aR or V1bR antagonism dose-dependently inhibited MAP after VP injection. V1aR or V1bR blockers at their ED50 doses did not alter baseline parameters in either control or CMS rats but attenuated the pressor response to VP microinjected into PVN by ∼50%. Combined V1aR and V1bR inhibition completely blocked the pressor response to PVN VP in control but not CMS rats. CMS rats required combined maximally inhibitory doses to block either endogenous VP within the PVN or responses to microinjected VP. Compared with unstressed control rats, CMS rats had higher plasma VP levels and greater abundance of V1aR and V1bR transcripts within PVN. Thus, the CMS rat model of depression results in higher resting MAP, heart rate, and RSNA, which can be mitigated by inhibiting vasopressinergic mechanisms involving both V1aR and V1bR within the PVN. Circulating VP may also play a role in the pressor response.

Fasting serum copeptin and asymptomatic peripheral artery disease: No association in patients with type 1 diabetes mellitus

OBJECTIVE

As copeptin is associated with lower-extremity amputation in patients with type 1 diabetes mellitus (T1DM), our study aimed to address the putative association between copeptin and asymptomatic peripheral artery disease (aPAD) in those patients.

DESIGN AND METHODS

This observational cross-sectional study included 112 patients with T1DM from a larger cohort (ClinicalTrials.gov: NCT02910271), selected (1:2) as per the presence of aPAD (n = 37) or not (n = 75). aPAD was evaluated by ankle-brachial index (ABI), toe-brachial index (TBI), and peripheral Doppler ultrasound. The two groups of patients were matched by age, gender distribution and duration of T1DM. Fasting serum copeptin was measured by high-sensitivity ELISA, and its relationships with clinical and biochemical variables as well as aPAD were evaluated too.

RESULTS

The study population was aged 42 ± 8 years, duration of T1DM was 27 ± 7 years, and mean HbA_1c was 7.7 ± 1.1%. No significant differences in copeptin concentrations were found between patients with or without aPAD (16.9 ± 10.8 vs 17.3 ± 14.7 pmol/L, respectively; P = 0.462). Considering all patients as a whole, copeptin correlated with systolic blood pressure (SBP; ρ = -0.209, P = 0.027), eGFR ρ = -0.271, P = 0.004), and serum sodium (ρ = -0.208, P = 0.027), but not with ABI (ρ = -0.068, P = 0.476). Stepwise multiple linear regression analysis (R²: 0.059; P = 0.035) retained SBP (β: -0.219, 95% CI: -1.391; -0.089) as the only significant predictor of copeptin concentration.

CONCLUSION

As serum copeptin does not appear to be associated with aPAD in patients with T1DM, further studies are now needed to elucidate whether it has any other potential role to play in the subclinical vascular disease of this patient population.

Plasma Copeptin and Risk of Lower-Extremity Amputation in Type 1 and Type 2 Diabetes

OBJECTIVE

Diabetes is the leading cause of nontraumatic lower-extremity amputations (LEAs). Identification of patients with foot ulcers at risk for amputation remains clinically challenging. Plasma copeptin, a surrogate marker of vasopressin, is associated with the risk of cardiovascular and renal complications in diabetes.

RESEARCH DESIGN AND METHODS

We assessed the association between baseline plasma copeptin and risk of LEA during follow-up in four cohorts of people with type 1 (GENESIS, n = 503, and GENEDIAB, n = 207) or type 2 diabetes (DIABHYCAR, n = 3,101, and SURDIAGENE, n = 1,452) with a median duration of follow-up between 5 and 10 years. Copeptin concentration was measured in baseline plasma samples by an immunoluminometric assay.

RESULTS

In the pooled cohorts with type 1 diabetes (n = 710), the cumulative incidence of LEA during follow-up by increasing tertiles (tertile 1 [TER1], TER2, and TER3) of baseline plasma copeptin was 3.9% (TER1), 3.3% (TER2), and 10.0% (TER3) (P = 0.002). Cox regression analyses confirmed the association of copeptin with LEA: hazard ratio (HR) for 1 SD increment of log[copeptin] was 1.89 (95% CI 1.28-2.82), P = 0.002. In the pooled cohorts of type 2 diabetes (n = 4,553), the cumulative incidence of LEA was 1.1% (TER1), 2.9% (TER2), and 3.6% (TER3) (P < 0.0001). In Cox regression analyses, baseline plasma copeptin was significantly associated with LEA: HR for 1 SD increment of log[copeptin] was 1.42 (1.15-1.74), P = 0.001. Similar results were observed in the cohort with type 2 diabetes for lower-limb revascularization (HR 1.20 [95% CI 1.03-1.39], P = 0.02).

CONCLUSIONS

Baseline plasma copeptin is associated with cumulative incidence of LEA in cohorts of people with both type 1 and type 2 diabetes and may help to identify patients at risk for LEA.

Central activation of the A1 adenosine receptor (A1AR) induces a hypothermic, torpor-like state in the rat

Since central activation of A1 adenosine receptors (A1ARs) plays an important role in the induction of the hypothermic and hypometabolic torpid state in hibernating mammals, we investigated the potential for the A1AR agonist N6-cyclohexyladenosine to induce a hypothermic, torpor-like state in the (nonhibernating) rat. Core and brown adipose tissue temperatures, EEG, heart rate, and arterial pressure were recorded in free-behaving rats, and c-fos expression in the brain was analyzed, following central administration of N6-cyclohexyladenosine. Additionally, we recorded the sympathetic nerve activity to brown adipose tissue; expiratory CO2 and skin, core, and brown adipose tissue temperatures; and shivering EMGs in anesthetized rats following central and localized, nucleus of the solitary tract, administration of N6-cyclohexyladenosine. In rats exposed to a cool (15°C) ambient temperature, central A1AR stimulation produced a torpor-like state similar to that in hibernating species and characterized by a marked fall in body temperature due to an inhibition of brown adipose tissue and shivering thermogenesis that is mediated by neurons in the nucleus of the solitary tract. During the induced hypothermia, EEG amplitude and heart rate were markedly reduced. Skipped heartbeats and transient bradycardias occurring during the hypothermia were vagally mediated since they were eliminated by systemic muscarinic receptor blockade. These findings demonstrate that a deeply hypothermic, torpor-like state can be pharmacologically induced in a nonhibernating mammal and that recovery of normothermic homeostasis ensues upon rewarming. These results support the potential for central activation of A1ARs to be used in the induction of a hypothermic, therapeutically beneficial state in humans.

Interaction of medullary P2 and glutamate receptors mediates the vasodilation in the hindlimb of rat

In the nucleus tractus solitarii (NTS) of rats, blockade of extracellular ATP breakdown to adenosine reduces arterial blood pressure (AP) increases that follow stimulation of the hypothalamic defense area (HDA). The effects of ATP on NTS P2 receptors, during stimulation of the HDA, are still unclear. The aim of this study was to determine whether activation of P2 receptors in the NTS mediates cardiovascular responses to HDA stimulation. Further investigation was taken to establish if changes in hindlimb vascular conductance (HVC) elicited by electrical stimulation of the HDA, or activation of P2 receptors in the NTS, are relayed in the rostral ventrolateral medulla (RVLM); and if those responses depend on glutamate release by ATP acting on presynaptic terminals. In anesthetized and paralyzed rats, electrical stimulation of the HDA increased AP and HVC. Blockade of P2 or glutamate receptors in the NTS, with bilateral microinjections of suramin (10 mM) or kynurenate (50 mM) reduced only the evoked increase in HVC by 75 % or more. Similar results were obtained with the blockade combining both antagonists. Blockade of P2 and glutamate receptors in the RVLM also reduced the increases in HVC to stimulation of the HDA by up to 75 %. Bilateral microinjections of kynurenate in the RVLM abolished changes in AP and HVC to injections of the P2 receptor agonist α,β-methylene ATP (20 mM) into the NTS. The findings suggest that HDA-NTS-RVLM pathways in control of HVC are mediated by activation of P2 and glutamate receptors in the brainstem in alerting-defense reactions.

Differential activation of adrenal, renal, and lumbar sympathetic nerves following stimulation of the rostral ventrolateral medulla of the rat

Under acute and chronic conditions, the sympathetic nervous system can be activated in a differential and even selective manner. Activation of the rostral ventrolateral medulla (RVLM) has been implicated in differential control of sympathetic outputs based on evidence primarily in the cat. Although several studies indicate that differential control of sympathetic outflow occurs in other species, only a few studies have addressed whether the RVLM is capable of producing varying patterns of sympathetic activation in the rat. Therefore, the purpose of the present study was to determine whether activation of the RVLM results in simultaneous and differential increases in preganglionic adrenal (pre-ASNA), renal (RSNA), and lumbar (LSNA) sympathetic nerve activities. In urethane-chloralose anesthetized rats, pre-ASNA, RSNA, and LSNA were recorded simultaneously in all animals. Microinjections of selected concentrations and volumes of glutamate increased pre-ASNA, RSNA, and LSNA concurrently and differentially. Pre-ASNA and RSNA (in most cases) exhibited greater increases compared with LSNA on a percentage basis. By varying the volume or location of the glutamate microinjections, we also identified individual examples of differential and selective activation of these nerves. Decreases in arterial pressure or bilateral blockade of RVLM GABA(A) receptors also revealed differential activation, with the latter having a 3- to 4-fold greater effect on sympathetic activity. Our data provide evidence that activation of the rat RVLM increases renal, lumbar, and preganglionic adrenal sympathetic nerve activities concurrently, differentially, and, in some cases, selectively.

Neural and humoral control of regional vascular beds via A1 adenosine receptors located in the nucleus tractus solitarii

Our previous studies showed that stimulation of adenosine A(1) receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and β-adrenergic vasodilation vs. sympathetic and vasopressinergic vasoconstriction. Because NTS A(1) adenosine receptors inhibit baroreflex transmission in the NTS and contribute to the pressor component of the HDR, we hypothesized that these receptors also contribute to the redistribution of blood from the visceral to the muscle vasculature via prevailing sympathetic and vasopressinergic vasoconstriction in the visceral (renal and mesenteric) vascular beds and prevailing β-adrenergic vasodilation in the somatic (iliac) vasculature. To test this hypothesis, we compared the A(1) adenosine-receptor-mediated effects of each vasoactive factor triggered by NTS A(1) adenosine receptor stimulation [N(6)-cyclopentyladenosine (CPA), 330 pmol in 50 nl] on the regional vascular responses in urethane/chloralose-anesthetized rats. The single-factor effects were separated using adrenalectomy, β-adrenergic blockade, V(1) vasopressin receptor blockade, and sinoaortic denervation. In intact animals, initial vasodilation was followed by large, sustained vasoconstriction with smaller responses observed in renal vs. mesenteric and iliac vascular beds. The initial β-adrenergic vasodilation prevailed in the iliac vs. mesenteric and renal vasculature. The large and sustained vasopressinergic vasoconstriction was similar in all vascular beds. Small sympathetic vasoconstriction was observed only in the iliac vasculature in this setting. We conclude that, although A(1) adenosine-receptor-mediated β-adrenergic vasodilation may contribute to the redistribution of blood from the visceral to the muscle vasculature, this effect is overridden by sympathetic and vasopressinergic vasoconstriction.

Muscle metaboreflex control of the circulation during exercise

This review covers the control of blood pressure, cardiac output and muscle blood flow by the muscle metaboreflex which involves chemically sensitive nerves located in muscle parenchyma activated by metabolites accumulating in the muscle during contraction. The efferent response to metaboreflex activation is an increase in sympathetic nerve activity that constricts the systemic vasculature and also evokes parallel inotropic and chronotropic effects on the heart to increase cardiac output. The metaboreflex elicits a significant blood pressure elevating response during exercise and functions to redistribute blood flow and blood volume. Regional specificity in the efferent response to the metaboreflex activated from either the leg or the arm is seen in the balance between signals for vasoconstriction to curtail blood flow and signals to increase cardiac output. The metaboreflex has dual functions. It can both elevate and decrease muscle blood flow depending on (1) the intensity and mode of contraction, (2) the limb in which the reflex is evoked, (3) the strength of the signal defined by the muscle mass, (4) the extent to which blood flow is redistributed from inactive vascular beds to increase central blood volume and (5) the extent to which cardiac output can be increased.

Increase in plasma ACTH induced by urethane is not a consequence of hyperosmolality

Although anesthetic doses of urethane increase plasma levels of ACTH, the exact mechanism through which this occurs is unclear. We theorized that these increases might be a consequence of an increased systemic osmolality owing to the large doses of urethane usually employed. To evaluate this possibility, we measured plasma osmolality and ACTH in a total of six rats after graded infusions of urethane (N=3 rats) or equimolar amounts of mannitol (N=3 rats). Rats received infusions at 15 min intervals up to a cumulative dose equivalent to an anesthetic dose for urethane (1.4 g/kg). Blood samples (0.35 ml) were withdrawn at baseline and 10 min after each infusion. Urethane and mannitol produced significant and equivalent increases in plasma osmolality. However, only urethane evoked increases in plasma ACTH which were maximal (252+/-55 pg/ml from a baseline of 27+/-7 pg/ml) after a cumulative dose of 1 g/kg. Thus, increases in plasma ACTH seen after anesthetic doses of urethane are unlikely to be a consequence of its effect on plasma osmolality.