The structural arteriolar changes in diabetes mellitus and essential hypertension. The relative contribution of ageing and high blood pressure

Sitting time is negatively related to microvascular endothelium-dependent function in rheumatoid arthritis

BACKGROUND

Sedentary behaviour is linked to increased cardiovascular disease risk in Rheumatoid Arthritis (RA), but the biological processes underlying this relationship are not understood.

OBJECTIVES

To investigate the cross-sectional associations of habitual sedentary behaviour, with endothelial function in RA.

METHODS

Sixty-eight RA patients (Mage = 55 ± 12 years) underwent Laser Doppler Imaging with iontophoresis, to assess microvascular endothelium-dependent (acetylcholine, ACh) and endothelium-independent (sodium nitroprusside, SNP) function. Large-vessel endothelium-dependent and endothelium-independent functions were measured via flow-mediated dilation (FMD) and glyceryl trinitrate dilation (GTN), respectively. Habitual sedentary behaviour (hours/week sitting) was self-reported (International Physical Activity Questionnaire).

RESULTS

Regressions revealed sitting time significantly negatively predicted microvascular endothelium-dependent function (ACh, _{unstandardized}β = -3.25, p = .02, 95% CI [-6.07, -.42], R² = 0.06), but did not associate with other endothelial function outcomes (SNP, FMD, GTN).

CONCLUSION

Habitual sedentary behaviour (sitting time) appears to be adversely linked to microvascular endothelium-dependent function among people living with RA.

Role of elevated EGFR phosphorylation in the induction of structural remodelling and altered mechanical properties of resistance artery from type 2 diabetic mice

BACKGROUND

Type 2 diabetes is associated with microvascular complications. We hypothesized that the sustained elevated EGFR phosphorylation produces structural wall remodelling and altered mechanical properties of mesenteric resistance artery (MRA) in type 2 diabetes.

METHODS

Freshly isolated MRA (80-100 microm diameter) from type 2 diabetic (db(-)/db(-), diabetic) and non-diabetic (db(-)/db(+), control) mice were subjected to pressure-passive diameter and wall thickness relationships; western blot analysis and immunohistology.

RESULTS

Data indicated that MRA from diabetic mice have a smaller passive diameter than MRA from control mice under intra-luminal pressure range from 25 to 125 mmHg. Measurements of wall thickness : lumen diameter ratios (21 +/- 1.8 vs 14 +/- 1.2 at 75 mmHg diabetic vs control, respectively), wall thickness and remodelling index (38 +/- 5% vs control) revealed eutrophic structural remodelling of MRA from diabetic mice, which was strengthened with histology. Mechanical properties revealed a great strain-stress relationship in MRA from control versus diabetic mice indicating increased stiffness in MRA from diabetic mice. Western blot analysis showed increased collagen type 1 content in a freshly isolated MRA from the type 2 diabetic mice when compared to control mice. Diabetic mice treated with EGFR inhibitor (AG1478, 10 mg/kg/day) for 2 weeks showed reduced EGFR phosphorylation, wall thickness, collagen type 1 content, and improved the altered mechanical properties of MRA.

CONCLUSION

These data provide evidence regarding the role of EGFR in morphological wall remodelling and altered mechanical properties of MRA from type 2 diabetic mice. This may identify new therapeutic targets for the control of vascular structure and therefore have important implications in type 2 diabetes.

Persistent Remodeling of Resistance Arteries in Type 2 Diabetic Patients on Antihypertensive Treatment

We hypothesized that resistance arteries from diabetic patients with controlled hypertension have less remodeling than vessels from untreated hypertensive subjects. Eight normotensive subjects (aged 44±3 years, 3 men; values are mean±SEM), 19 untreated hypertensive subjects (46±2 years, 9 men), and 23 hypertensive subjects with type 2 diabetes mellitus under antihypertensive treatment (58±1 years, 15 men) were studied. Resistance arteries dissected from gluteal subcutaneous tissue were assessed on a pressurized myograph. Most diabetic patients (70%) were being treated with angiotensin-converting enzyme inhibitors. Although systolic blood pressure was still above the normotensive range in these patients (144±2 versus 150±3 mm Hg in hypertensive and 114±4 mm Hg in normotensive subjects), diastolic blood pressure was well controlled (83±2 mm Hg) and significantly lower compared with that in untreated hypertensives (100±1 mm Hg; P <0.001) but higher than in normotensives (76±3 mm Hg; P <0.05). Thus, pulse pressure was higher in diabetic patients ( P <0.05). The media-to-lumen ratio of resistance arteries was greater in hypertensives (0.083±0.002) compared with normotensive controls (0.059±0.003; P <0.05) and was even higher in diabetic hypertensive subjects (0.105±0.004; P <0.001 versus normotensive controls). The medial cross-sectional area was greater in diabetic and hypertensive patients compared with normotensive controls ( P <0.001). Acetylcholine-induced relaxation was impaired in vessels from hypertensive patients and from patients with both diabetes mellitus and hypertension ( P <0.05 versus normotensive controls), whereas endothelium-independent vasorelaxation was similar in all groups. Despite effective antihypertensive treatment, resistance arteries from hypertensive diabetic patients showed marked remodeling, greater than that of vessels from untreated, nondiabetic, hypertensive subjects, in agreement with the high cardiovascular risk of subjects suffering from both diabetes and hypertension.

Vascular structural and functional changes in type 2 diabetes mellitus: evidence for the roles of abnormal myogenic responsiveness and dyslipidemia

BACKGROUND

To further investigate vascular morphology and function in type 2 (non-insulin-dependent) diabetes mellitus (type 2D), small arteries were examined in vitro from carefully defined cohorts of patients with or without concomitant hypertension and the results compared with those from selected normotensive nondiabetic control subjects and a group of untreated patients with essential hypertension (EH).

METHODS AND RESULTS

Blood vessels were studied through the use of pressure myography to determine vascular morphology, mechanics, and myogenic responsiveness, together with testing of constrictor and dilator function. Small arteries from patients with EH demonstrated eutrophic inward remodeling and an increased distensibility. Vessels from type 2D patients demonstrated hypertrophy, a further increase in distensibility, and a highly significant loss of myogenic responsiveness compared with patients with EH and control patients. Vasoconstrictor function to norepinephrine was normal in patients with type 2D and type 2D+H and EH. Endothelium-dependent dilation was normal in patients with EH but abnormal in patients with type 2D and type 2D+H. There was a significant correlation between dilator impairment and the degree of dyslipidemia recorded in all groups.

CONCLUSIONS

These results demonstrate vascular hypertrophy in small arteries from patients with type 2D. This could be a consequence of impaired myogenic responsiveness, which will increase wall stress for a given intraluminal pressure, which may be a stimulus for vascular hypertrophy. A substantial proportion of endothelial dysfunction can be attributed to an effect of the abnormal lipid profile seen in such patients.

Delayed wound healing in aged rats is associated with increased collagen gel remodeling and contraction by skin fibroblasts, not with differences in apoptotic or myofibroblast cell populations

Aging has been anecdotally reported to result in prolonged wound healing. Measurement of punch biopsy wound closure in young (4 month old) and old (36 month old) rats indicated there was a significant delay in wound closure by old rats during the early phase of repair, after which closure rates were equivalent. The delay in granulation tissue accumulation in older animals could involve premature programmed cell death (apoptosis); however, apoptotic fibroblasts in sponge granulation tissue and tissue culture were less abundant in samples from old rats relative to young rats. Myofibroblasts express alpha-smooth muscle actin, and they are believed to be important in wound contraction. There were no significant differences in overall abundance or distribution of alpha-smooth muscle actin containing myofibroblasts in granulation tissue and in cultured granulation tissue fibroblasts regardless of the age of the donor rat. The spatial distribution of myofibroblasts and apoptotic cells was distinct. Fibroblasts from granulation tissue and skin explants were placed in a collagen gel contraction assay prior to the 5th passage to determine their in vitro contractility. While granulation tissue fibroblasts from young and old rats showed similar collagen gel contractility, skin fibroblasts from old rats displayed greater collagen gel contractile behavior than young skin fibroblasts. Greater gel contractility of fibroblasts from old rats appeared to result, in large part, from the ability of those cells to cause generalized gel degradation. Gelatin zymography indicated a greater abundance of matrix metalloproteinase-2 in supernatants from gels containing skin fibroblasts from old rats. Taken together, these results suggest that the age-associated healing delay in the rat may not be related to the appearance or abundance of distinct myofibroblast or apoptotic cell populations. Proteolysis may have a significant role in delayed wound healing in aged animals.

Structural alterations in subcutaneous small arteries of normotensive and hypertensive patients with non-insulin-dependent diabetes mellitus

BACKGROUND

It is not presently known whether non-insulin-dependent diabetes mellitus (NIDDM) is associated with the presence of structural alterations in small arteries or whether the combination of hypertension and NIDDM may have an additive effect on endothelial dysfunction. Therefore, we investigated subcutaneous small arteries in 12 normotensive subjects (NT group), 18 patients with essential hypertension (EH group), 13 patients with NIDDM, and 11 patients with NIDDM and EH (NIDDM+EH group).

METHODS AND RESULTS

Subcutaneous small arteries were evaluated by a micromyographic technique. The internal diameter, the media-to-lumen ratio, remodeling and growth indices, and the collagen-to-elastin ratio were calculated. Concentration-response curves to acetylcholine, bradykinin, the endothelium-independent vasodilator sodium nitroprusside, and endothelin-1 were performed. The media-to-lumen ratio was higher in the EH, NIDDM, and NIDDM+EH groups compared with the NT group. EH patients showed the presence of eutrophic remodeling, whereas NIDDM and NIDDM+EH patients showed 40% to 46% cell growth. The collagen-to-elastin ratio was significantly increased in the EH and NIDDM+EH groups compared with the NT group. The vasodilatation to acetylcholine and bradykinin was similarly reduced in EH, NIDDM, and NIDDM+EH groups compared with the NT group. The contractile responses to endothelin-1 were similarly reduced in EH, NIDDM, and NIDDM+EH patients.

CONCLUSIONS

Our data suggest that the effects of NIDDM and EH on small artery morphology are quantitatively similar but qualitatively different and that the presence of hypertension in diabetic patients has little additive effect on small artery morphology and none on endothelial dysfunction.