Intermittent parathyroid hormone administration attenuates endothelial dysfunction in old rats

Normal parathyroid hormone and non-proliferative diabetic retinopathy in patients with type 2 diabetes

AIMS/INTRODUCTION

To investigate the associations between parathyroid hormone (PTH) and non-proliferative diabetic retinopathy (NPDR) in patients with type 2 diabetes mellitus.

MATERIALS AND METHODS

Data were collected from 2,322 patients with type 2 diabetes mellitus in hospital between 2017 and 2019. The odds ratio (OR) and the corresponding 95% confidence interval related to the quartiles of PTH were obtained by logistic regression analysis after adjusting the potential confounding variation.

RESULTS

The patients were stratified into quartiles (Q1-Q4) based on the PTH levels, with the cut-off limits of ≤23.74, 23.74-29.47, 29.47-37.30 and >37.30 pg/mL in men, and ≤24.47, 24.47-31.22, 31.22-39.49 and >39.49 pg/mL in women. The first quartile (Q1) represents the lowest quartile and the fourth quartile (Q4) is the highest. According to the quartiles (Q1-Q4), the prevalence rate of NPDR in patients showed a significantly decreasing trend (37.9%, 36.3%, 34.0% vs 24.0% in men; 43.2%, 40.5%, 31.1% vs 26.2% in women, both P < 0.05). Independent of age, diabetes duration and other metabolic factors, multivariate logistic regression showed that participants in Q4 had a lower OR of NPDR than those in Q1 (OR 0.443, 95% confidence interval 0.300-0.654, P < 0.001 for men; OR 0.428, 95% confidence interval 0.283-0.646, P < 0.001 for women).

CONCLUSIONS

Low serum PTH levels were significantly associated with complications of NPDR in inpatients. Its causality remains to be further studied.

Bone Marrow Microvasculature

The skeleton is highly vascularized due to the various roles blood vessels play in the homeostasis of bone and marrow. For example, blood vessels provide nutrients, remove metabolic by-products, deliver systemic hormones, and circulate precursor cells to bone and marrow. In addition to these roles, bone blood vessels participate in a variety of other functions. This article provides an overview of the afferent, exchange and efferent vessels in bone and marrow and presents the morphological layout of these blood vessels regarding blood flow dynamics. In addition, this article discusses how bone blood vessels participate in bone development, maintenance, and repair. Further, mechanical loading-induced bone adaptation is presented regarding interstitial fluid flow and pressure, as regulated by the vascular system. The role of the sympathetic nervous system is discussed in relation to blood vessels and bone. Finally, vascular participation in bone accrual with intermittent parathyroid hormone administration, a medication prescribed to combat age-related bone loss, is described and age- and disease-related impairments in blood vessels are discussed in relation to bone and marrow dysfunction. © 2020 American Physiological Society. Compr Physiol 10:1009-1046, 2020.

Elevated Circulating Trimethylamine N-Oxide Levels Contribute to Endothelial Dysfunction in Aged Rats through Vascular Inflammation and Oxidative Stress

Vascular endothelial dysfunction, a characteristic of the aging process, is an important risk factor for cardiovascular disease in aging. Although, vascular inflammation and oxidative stress are major contributors to endothelial dysfunction in aging, the underlying mechanisms during the aging process are not fully understood. Accumulating evidence reveals that gut microbiota-dependent metabolite trimethylamine-N-oxide (TMAO) is implicated in the pathogenesis of many cardiovascular diseases. We tested the hypothesis that aging increases circulating TMAO levels, which induce vascular inflammation and oxidative stress, resulting in age-associated endothelial dysfunction. Old (22-mo-old) and young (4-mo-old) Fischer-344 rats were treated without (control) or with 1.0% 3,3-Dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) in drinking water for 8 weeks. Compared with young control group, old control group had markedly higher plasma TMAO levels, which were reduced by DMB treatment. Endothelium-dependent relaxation of aorta in response to acetylcholine was impaired in old control group compared with young control group as indicated by decreased maximal relaxation (E_max) and reduced area under the curve (AUC). E_max and AUC were both normalized in old rats treated with DMB. No difference in endothelial-independent relaxation in response to sodium nitroprusside was observed among groups. Molecular studies revealed that old control group exhibits increased expression of proinflammatory cytokines and superoxide production, and decreased expression of endothelial nitric-oxide synthase (eNOS) in the aorta, all of which were restored by DMB treatment. These results suggest that aging increases circulating TMAO levels, which may impair eNOS-derived NO bioavailability by increasing vascular inflammation and oxidative stress, contributing to aging-associated endothelial dysfunction.