Michelle L. Harrison

Background: In type 2 diabetes mellitus (T2DM), bone and microvascular complications may be linked. Methods: The University of California Davis (UCD) polygenic T2DM and Sprague Dawley healthy control (CTL) rats (N = 48) were divided equally into diabetic and age-matched groups: (1) pre-diabetes, (2) diabetes onset, (3) early-stage T2DM, and (4) late-stage T2DM. Body mass, HbA1c, fasted blood glucose and femoral and tibial lengths were measured. Bones were scanned (μCT; 15 µm) to assess trabecular microarchitecture and density and mid-shaft cortical thickness (Ct.Th, µm), density and porosity. Ossified vessel volume (OsVV, %) and thickness (OsV.Th, µm) were also analyzed. A GLM determined significance at p < 0.05. Body mass and HbA1c were higher (p < 0.05) in all T2DM groups and blood glucose became elevated (p < 0.05) in early-stage T2DM and late-stage T2DM. Results: Tibiae and femora were longer (p < 0.05) with diabetes. Tibial bone volume was lower (p < 0.05) in pre-diabetes (4 ± 1% vs. CTL, 9 ± 2%) and late-stage T2DM (5 ± 2% vs. CTL, 8 ± 2%), and femoral bone volume was lower (p < 0.05) in pre-diabetes (7 ± 1% vs. 12 ± 4%). Cortical density (tibia) was lower (p < 0.05) in pre-diabetes and early-stage T2DM. Trabecular density in the femur was lower (p < 0.05) in all T2DM groups and cortical density was reduced (p < 0.05) in pre-diabetes, diabetes onset, and late-stage T2DM. OsVV in both bones were lower (p < 0.05) during early-stage T2DM. Tibial OsV.Th was higher (p < 0.05) in pre-diabetes (69 ± 14 µm vs. CTL, 56 ± 13 µm) and late-stage T2DM (80 ± 10 µm vs. CTL, 59 ± 13 µm) and higher (p < 0.05) in the femur at diabetes onset (58 ± 14 µm vs. CTL, 40 ± 10 µm). Conclusions: Trabecular and cortical bone varied as diabetes progressed, and the thicker ossified vessels may represent microangiopathy.

An exaggerated exercise pressor reflex and peripheral neuropathy are both evoked by the same type of thinly myelinated afferents and are present in patients with type 2 diabetes mellitus (T2DM). Although it is known that the pro‐inflammatory cytokine interleukin‐1β (IL‐1β) contributes to peripheral neuropathy, the effects of IL‐1β on the exercise pressor reflex in T2DM are not known. Therefore, we aimed to determine the effect of IL‐1 receptors on the exercise pressor reflex in T2DM. We compared changes in peak pressor (mean arterial pressure; ΔMAP), blood pressure index (ΔBPi), heart rate (ΔHR) and heart rate index (ΔHRi) responses to static and intermittent contractions and tendon stretch before and after peripheral IL‐1 type 1 receptor blockade (anakinra, Kineret ^® ) in T2DM and healthy male rats and IL‐1 receptor activation (IL‐1β) in healthy rats. Blocking IL‐1 receptors significantly attenuated the ΔMAP and ΔBPi to static contraction in T2DM rats. Furthermore, blocking IL‐1 receptors significantly attenuated the ΔMAP, ΔBPi and ΔHRi to intermittent contraction, and ΔMAP to tendon stretch in T2DM rats (all P < 0.05). In addition, IL‐1 receptor activation significantly exaggerated the ΔMAP and ΔBPi to static contraction and ΔMAP, ΔBPi and ΔHR to intermittent contraction in healthy rats, all P < 0.05. Furthermore, circulating IL‐1β serum concentrations were significantly greater in T2DM rats than in healthy rats ( P < 0.05). We conclude that IL‐1 signalling contributes to the exaggerated exercise pressor reflex in T2DM, suggesting for the first time that inflammatory cytokines play a critical role in exaggerated blood pressure responses to exercise in those with T2DM. image Key points: Chronic inflammation, a complication of type 2 diabetes mellitus (T2DM), causes increased production of pro‐inflammatory cytokines, such as interleukin (IL)‐1β, IL‐6, and tumour necrosis factor‐α. IL‐1β has been shown to sensitize muscle afferents that conduct the exercise pressor reflex. We found blocking of IL‐1 receptors by anakinra (Kineret ^® ), an IL‐1 type 1 receptor antagonist, significantly attenuated the exaggerated exercise pressor reflex in T2DM rats, but not in healthy rats. In addition, activating IL‐1 receptors with IL‐1β significantly augmented the exercise pressor reflex in healthy rats. Our findings suggest that IL‐1 receptors, by mediating IL‐1β signalling, play a role in exaggerating the exercise pressor reflex in T2DM. These results highlight the complex interplay between inflammation and the autonomic nervous system in regulating cardiovascular function, and the potential for using an FDA‐approved IL‐1 receptor antagonist, Kineret ^® , as a therapeutic approach to reduce adverse cardiovascular events during physical activity in those with T2DM.

We compared the pressor and cardioaccelerator responses to static muscle contraction before and after inhibition of cyclooxygenase (COX) activity within the contracting hindlimb in decerebrate, unanesthetized type 2 diabetic mellitus (T2DM) and healthy rats. The pressor responses to muscle contraction were attenuated after peripheral inhibition of COX activity in T2DM but not in healthy rats. We concluded that COX products partially contribute to the exaggerated pressor reflex in those with T2DM.

There are many barriers to physical activity among cancer survivors. Survivors treated with neurotoxic chemotherapy may develop chemotherapy-induced peripheral neuropathy (CIPN) and experience additional barriers related to sensorimotor and mobility deficits. This study examined physical activity behaviors, including physical activity predictors, among cancer survivors treated with neurotoxic chemotherapies. A cross-sectional study of 252 participants, 3-24 months after neurotoxic chemotherapy, was undertaken. Physical activity was self-reported (IPAQ). CIPN was self-reported (FACT/GOG-Ntx-13), clinically graded (NCI-CTCAE), and objectively measured using neurological grading scales and neurophysiological techniques (tibial and sural nerve conduction studies). Balance (Swaymeter) and fine motor skills (grooved pegboard) were assessed. Regression models were used to identify clinical, demographic and CIPN predictors of walking and moderate-vigorous physical activity. Forty-four percent of participants did not meet recommended physical activity guidelines (≥150 min/week). Sixty-six percent presented with CIPN. Nineteen percent of participants with CIPN reported that symptoms interfered with their ability to be physically active. A lower proportion of survivors aged ≥60, with grade ≥1 CIPN or BMI ≥30, reported meeting physical activity guidelines (all p < .05). Regression models identified older age, higher BMI, and patient-reported CIPN associated with lower walking, while higher BMI and females were associated with lower moderate-vigorous physical activity. Neurologically assessed CIPN did not associate with walking or moderate-vigorous physical activity. Cancer survivors exposed to neurotoxic chemotherapy have low physical activity levels. Further work should examine the factors causing physical activity limitations in this cohort and designing interventions to improve physical function and quality of life in survivors.

Emerging evidence suggests the exercise pressor reflex is exaggerated in early stage type 1 diabetes mellitus (T1DM). Piezo channels may play a role in this exaggeration, as blocking these channels attenuates the exaggerated pressor response to tendon stretch in T1DM rats. However, tendon stretch constitutes a different mechanical and physiological stimuli than that occurring during muscle contraction. Therefore, the purpose of this study was to determine the contribution of Piezo channels in evoking the pressor reflex during an intermittent muscle contraction in T1DM. In unanesthetized decerebrate rats, we compared the pressor and cardioaccelerator responses to intermittent muscle contraction before and after locally injecting grammostola spatulata mechanotoxin 4 (GsMTx-4, 0.25 µM) into the hindlimb vasculature. Although GsMTx-4 has a high potency for Piezo channels, it has also been suggested to block transient receptor potential cation (TRPC) channels. We, therefore, performed additional experiments to control for this possibility by also injecting SKF 96365 (10 µM), a TRPC channel blocker. We found that local injection of GsMTx-4, but not SKF 96365, attenuated the exaggerated peak pressor (ΔMAP before: 33 ± 3 mmHg, after: 22 ± 3 mmHg, P = 0.007) and pressor index (ΔBPi before: 668 ± 91 mmHg·s, after: 418 ± 81 mmHg·s, P = 0.021) response in streptozotocin (STZ) rats (n = 8). GsMTx-4 attenuated the exaggerated early onset pressor and the pressor response over time, which eliminated peak differences as well as those over time between T1DM and healthy controls. These data suggest that Piezo channels are an effective target to normalize the exercise pressor reflex in T1DM. NEW & NOTEWORTHY This is the first study to demonstrate that blocking Piezo channels is effective in ameliorating the exaggerated exercise pressor reflex evoked by intermittent muscle contraction, commonly occurring during physical activity, in T1DM. Thus, these findings suggest Piezo channels may serve as an effective therapeutic target to reduce the acute and prolonged cardiovascular strain that may occur during dynamic exercise in T1DM.

This is the first study to provide evidence that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated exercise pressor reflex evoked by intermittent muscle contraction, resulting in substantially higher cardiovascular strain. These findings are significant as they indicate that interventions targeting the exercise pressor reflex may work to alleviate the increased cardiovascular strain and overall burden during exercise in T1DM.

Patients with type-2 diabetes mellitus (T2DM) have exaggerated sympathetic activity and blood pressure responses to exercise. However, the underlying mechanisms for these responses, as well as how these responses change throughout disease progression, are not completely understood. For this study, we examined the effect of the progression of T2DM on the exercise pressor reflex, a critical neurocardiovascular mechanism that functions to increase sympathetic activity and blood pressure during exercise. We also aimed to examine the effect of T2DM on reflexive cardiovascular responses to static contraction, as well as those responses to tendon stretch when an exaggerated exercise pressor reflex was present. We evoked the exercise pressor reflex and mechanoreflex by statically contracting the hindlimb muscles and stretching the Achilles tendon, respectively, for 30 s. We then compared pressor and cardioaccelerator responses in unanesthetized, decerebrated University of California Davis (UCD)-T2DM rats at 21 and 31 wk following the onset of T2DM to responses in healthy nondiabetic rats. We found that the pressor response to static contraction was greater in the 31-wk T2DM [change in mean arterial pressure (∆MAP) = 39 ± 5 mmHg] but not in the 21-wk T2DM (∆MAP = 24 ± 5 mmHg) rats compared with nondiabetic rats (∆MAP = 18 ± 2 mmHg; P < 0.05). Similarly, the pressor and the cardioaccelerator responses to tendon stretch were significantly greater in the 31-wk T2DM rats [∆MAP = 69 ± 6 mmHg; change in heart rate (∆HR) = 28 ± 4 beats/min] compared with nondiabetic rats (∆MAP = 14 ± 2 mmHg; ∆HR = 5 ± 3 beats/min; P < 0.05). These findings suggest that the exercise pressor reflex changes as T2DM progresses and that a sensitized mechanoreflex may play a role in exaggerating these cardiovascular responses. NEW & NOTEWORTHY This is the first study to provide evidence that as type-2 diabetes mellitus (T2DM) progresses, the exercise pressor reflex becomes exaggerated, an effect that may be due to a sensitized mechanoreflex. Moreover, these findings provide compelling evidence suggesting that impairments in the reflexive control of circulation contribute to exaggerated blood pressure responses to exercise in T2DM.

Recent findings have shown that muscle contraction evokes an exaggerated pressor response in type 1 diabetes mellitus (T1DM) rats; however, it is not known whether the mechanoreflex, which is commonly stimulated by stretching the Achilles tendon, contributes to this abnormal response. Furthermore, the role of mechano-gated Piezo channels, found on thin-fiber afferent endings, in evoking the mechanoreflex in T1DM is also unknown. Therefore, in male and female streptozotocin (STZ, 50 mg/kg)-induced T1DM and healthy control (CTL) rats, we examined the pressor and cardioaccelerator responses to tendon stretch during the early stage of the disease. To determine the role of Piezo channels, GsMTx-4, a selective Piezo channel inhibitor, was injected into the arterial supply of the hindlimb. At 1 wk after STZ injection in unanesthetized, decerebrate rats, we stretched the Achilles tendon for 30 s and measured pressor and cardioaccelerator responses. We then compared pressor and cardioaccelerator responses to tendon stretch before and after GsMTx-4 injection (10 µg/100 ml). We found that the pressor (change in mean arterial pressure) response [41 ± 5 mmHg ( n = 15) for STZ and 18 ± 3 mmHg ( n = 11) for CTL ( P < 0.01)] and cardioaccelerator (change in heart rate) response [18 ± 4 beats/min for STZ ( n = 15) and 8 ± 2 beats/min ( n = 11) for CTL ( P < 0.05)] to tendon stretch were exaggerated in STZ rats. Local injection of GsMTx-4 attenuated the pressor [55 ± 7 mmHg ( n = 6) before and 27 ± 9 mmHg ( n = 6) after GsMTx-4 ( P < 0.01)], but not the cardioaccelerator, response to tendon stretch in STZ rats and had no effect on either response in CTL rats. These data suggest that T1DM exaggerates the mechanoreflex response to tendon stretch and that Piezo channels play a role in this exaggeration.

Chronic immune activation and ensuing inflammation that accompany HIV infection lead to adverse metabolic consequences and an increased risk of type 2 diabetes (T2D). We examined the additive effects of T2D on circulating biomarkers involved in inflammation, coagulation, and vascular function along with plasma amino acids in people living with HIV (PLWH). This cross-sectional study included PLWH with and without T2D (n = 32 total). Analyses involved a multiplex platform for circulating biomarkers and gas chromatography–vacuum ultraviolet spectroscopy for plasma amino acids. In PLWH and T2D, both fibrinogen (2.0 ± 0.6 vs 1.6 ± 0.4 µg/mL, p = 0.02) and von Willebrand factor (vWF) (40.8 ± 17.2 vs 26.7 ± 13.8 µg/mL, p = 0.02) were increased and tryptophan (47 ± 6 vs 53 ± 8 nmol/mL, p = 0.03) and threonine (102 ± 25 vs 125 ± 33 nmol/mL, p = 0.03) were decreased. Fibrinogen, as a biomarker of inflammation, and vWF, as a biomarker of endothelial dysfunction, are augmented by the combined effects of HIV and T2D and may contribute to the pathogenesis of T2D in PLWH. Chronic immune activation and inflammation compromise the integrity of the intestinal mucosa, which increases mucus production. Tryptophan metabolism is altered by a loss of intestinal membrane integrity and threonine is consumed in the production of mucus. Metabolic competition arising from increased protein synthesis in the setting of chronic inflammation along with the associated loss in intestinal membrane integrity may be a primary mechanism in the pathogenesis of T2D in PLWH and requires further investigation.