John H. Krege

A Noninvasive Computerized Tail-Cuff System for Measuring Blood Pressure in Mice

We have validated a noninvasive computerized tail-cuff system for measuring blood pressure in mice. The system was designed to perform all functions automatically, including a programmable routine of cuff inflation and deflation, analysis and assignment of pulse rate and blood pressure, and recording of data electronically. To evaluate this system over a range of blood pressures, we gave groups of mice enalapril or NG-nitro-L-arginine methyl ester in their drinking water. For each of these groups, an equal number of control mice were given nothing in their drinking water. Tail-cuff blood pressures were recorded as the means of blood pressures determined on at least 3 days after at least 7 days of training. Tail-cuff enalapril and control group means were measured both 3 and 4 months after enalapril (or no drug) was begun; the group means at 3 months were not significantly different from the group means at 4 months. These results demonstrate that the system gives reproducible results. After the tail-cuff measurements were completed, intra-arterial blood pressures were attempted in all mice under unrestrained, unanesthetized conditions, and individual mouse (n = 22) blood pressures with the use of the two methods were compared. The blood pressures from individual mice by tail-cuff and intra-arterial methods were highly correlated (r = .86, P < .01). The means for the four mouse groups were also highly correlated (r = .98, P < .02).(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogen receptor α is a major mediator of 17β-estradiol’s atheroprotective effects on lesion size in Apoe–/– mice

The inhibitory effects of estrogen (17β-estradiol) on atherosclerosis have been well documented in numerous animal models, and epidemiological evidence supports this protective effect in humans. The detailed mechanisms for this protection are not understood, but most are thought to be mediated through estrogen receptors (ERs), of which two are known (ERα and ERβ). To investigate the role of ERα in the atheroprotective effect of 17β-estradiol (E2), we ovariectomized female mice that lack apoE (AAee) or lack both apoE and ERα (ααee), and treated half of them with E2 for three months. E2 treatment of ovariectomized AAee females dramatically reduced the size of the lesions as well as their histological complexity. Plasma cholesterol was significantly reduced in this group, although the observed extent of protection by E2 was greater than could be explained solely by the change in lipid levels. In contrast, E2 treatment of ovariectomized ααee females caused minimal reduction in lesion size and no reduction in total plasma cholesterol compared with ααee mice without E2, demonstrating that ERα is a major mediator of the atheroprotective effect of E2. Nevertheless, E2 treatment significantly reduced the complexity of plaques in the ααee females, although not to the same degree as in AAee females, suggesting the existence of ERα-independent atheroprotective effects of E2.

Angiotensin-Converting Enzyme Gene Mutations, Blood Pressures, and Cardiovascular Homeostasis

A common polymorphism of the angiotensin-converting enzyme (ACE) gene (ACE in humans, Ace in mice) is associated with differences in circulating ACE levels that may confer a differential risk for cardiovascular diseases. To study the effects of genetically determined changes in Ace gene function within a defined genetic and environmental background, we have studied mice having one, two, or three functional copies of the Ace gene at its normal chromosomal location. ACE activities in the serum increased progressively from 62% of normal in the one-copy animals to 144% of normal in the three-copy animals (P < 10(-15), n = 132). The blood pressures of the mice having from one to three copies of the Ace gene did not differ significantly, but the heart rates, heart weights, and renal tubulointerstitial volumes decreased significantly with increasing Ace gene copy number. The level of kidney renin mRNA in the one-copy mice was increased to 129 +/- 9% relative to that of the normal two-copy mice (100 +/- 4%, P = .01, n = 16). We conclude that significant homeostatic adaptations successfully normalize the blood pressures of mice that have quantitative changes in Ace gene function. Our results suggest only that quantitative changes in expression of the Ace gene will observably affect blood pressures when accompanied by additional environmental or genetic factors that together with Ace exceed the capacity of the homeostatic mechanisms.

Genetically increased angiotensin I-converting enzyme level and renal complications in the diabetic mouse

Diabetic nephropathy is a major risk factor for end-stage renal disease and cardiovascular diseases and has a marked genetic component. A common variant (D allele) of the angiotensin Iconverting enzyme (ACE) gene, determining higher enzyme levels, has been associated with diabetic nephropathy. To address causality underlying this association, we induced diabetes in mice having one, two, or three copies of the gene, normal blood pressure, and an enzyme level range (65–162% of wild type) comparable to that seen in humans. Twelve weeks later, the three-copy diabetic mice had increased blood pressures and overt proteinuria. Proteinuria was correlated to plasma ACE level in the three-copy diabetic mice. Thus, a modest genetic increase in ACE levels is sufficient to cause nephropathy in diabetic mice.

Aberrant Renal Vascular Morphology and Renin Expression in Mutant Mice Lacking Angiotensin-Converting Enzyme

To determine whether angiotensin-converting enzyme plays a role in the development and maintenance of normal renal architecture, the renal morphology of 10- to 12-month-old female mice homozygous for a disruption of the converting enzyme gene was compared with that of age-matched wild-type mice. Tubular obstruction, dilatation, and atrophy were present in all kidneys from the homozygous mutant mice but absent in wild types; two kidneys from 4 mutant mice but none from the wild types were hydronephrotic. The entire arterial vascular tree, microdissected from mice with no converting enzyme, was grossly distorted in comparison to the vasculature of wild-type mice; all intrarenal arterial vessels were widened and thickened, including the terminal (afferent) arterioles. In wild-type mice kidneys, renin-positive cells were detected exclusively in a juxtaglomerular localization. In contrast, abnormal distribution of renin immunostaining was observed in mice without converting enzyme; scattered renin-positive cells were seen along the arterial vessels, often in a perivascular localization, and interstitial renin-positive cells surrounded glomeruli. Kidney renin mRNA was increased more than 32-fold in the mutant mice compared with wild types. Northern blot analysis revealed that this increase included the accumulation of large amounts of smaller renin RNA transcripts. In summary, mice lacking the converting enzyme exhibit abnormal renal vessels and tubules. Renin synthesis is increased, accompanied by the presence of small renin mRNA species, and renin is present mainly in interstitial and perivascular cells. We conclude that angiotensin-converting enzyme is necessary to preserve normal kidney architecture and the normal pattern of renin expression.

PINP as an aid for monitoring patients treated with teriparatide

Biochemical markers of bone turnover may be useful aids for managing patients with osteoporosis. A 12-month, phase 3, multicenter trial of Japanese patients at high risk of fracture was conducted to assess the effects of teriparatide 20 μg/day on BMD, serum markers of bone turnover, and safety. Two-hundred and seven subjects (93% female; median age 70 years) were randomized in double-blind fashion 2:1 to teriparatide versus placebo. Bone turnover markers including procollagen type I N-terminal propeptide (PINP), bone-specific alkaline phosphatase (bone ALP) and type I collagen cross-linked C-telopeptide (CTX) were collected at baseline, 1, 3, 6, and 12 months. Lumbar spine, femoral neck, and total hip BMD were measured at baseline, 3, 6, and 12 months. Increases in PINP at 1 month correlated best with increases in lumbar spine BMD at 12 months (r=0.76; P<0.01). The proportions of patients with an increase from baseline in PINP >10 μg/L at 1, 3, and 6 months were 3%, 0%, and 2% in the placebo, and 93%, 87%, and 83% in the teriparatide group. The proportions of patients with an increase in PINP >10 μg/L at either 1 or 3 months were 3% in the placebo and 95% in the teriparatide group (P<0.001). The proportions of patients with a significant increase in lumbar spine BMD (increase from baseline ≥3%) at 12 months were 20% in the placebo and 94% in the teriparatide group. The proportions of patients with an increase in PINP >10 μg/L at 1 or 3 months and an increase in lumbar spine BMD ≥3% at 12 months was 0% of placebo group patients and 92% of teriparatide group patients (P<0.001). These data confirm a strong relationship between early change in PINP and later change in lumbar spine BMD during teriparatide therapy. Also, these results suggest that monitoring with PINP and lumbar spine BMD successfully identifies positive responses in most patients taking teriparatide and negative responses in most patients not taking teriparatide. PINP monitoring may be a useful aid in the management of patients with osteoporosis during teriparatide treatment.

Blood Pressures and Cardiovascular Homeostasis in Mice Having Reduced or Absent Angiotensin-Converting Enzyme Gene Function

We studied cardiovascular phenotypes in wild-type (+/+), heterozygous (+/-), and homozygous mutant (-/-) mice for an insertional inactivation of the angiotensin-converting enzyme (ACE) gene (Ace in mice, ACE in humans). Compared with +/+ mice, baseline mean arterial pressure was not significantly altered in +/- mice but was reduced by 51+/-4 mm Hg in -/- mice. Although the pressor response to injected angiotensin II did not differ significantly in the three genotypic groups, the pressor response to angiotensin I was strongly affected by Ace genotype: Compared with the response in the +/+ group (+26% of baseline), the response to Ang I was close to half normal (+12%) in the +/- group and virtually abolished (+1%) in the -/- group. The depressor response to injected bradykinin was significantly enhanced in the +/- and -/- groups compared with the +/+ group. Ace expression and ACE activity were directly related to functional Ace copy number, and renin and angiotensinogen mRNA levels were inversely related to Ace copy number. Angiotensin type 1A receptor mRNA levels were not significantly different in the +/+, +/-, and -/- groups. We conclude that (1) ACE is essential for the maintenance of normal blood pressure; (2) subnormal levels of ACE affect the blood pressure responses to infused angiotensin I and bradykinin in vivo; and (3) compensations for inactivation of one Ace copy, which include increased expression of renin, normalize blood pressure in heterozygotes.

Bone formation markers in patients with glucocorticoid-induced osteoporosis treated with teriparatide or alendronate☆

Reduced osteoblast function is a primary defect in glucocorticoid-induced osteoporosis (GIO), and is reflected by decreased biochemical markers of bone formation, such as serum osteocalcin (OC) and procollagen type I N-terminal propeptide (PINP). This analysis compared the effects of teriparatide and alendronate on OC and PINP in patients with GIO. In a double-blind study, women (N=159) and men (N=38) with GIO were randomized to either teriparatide 20 mug/day by subcutaneous injection or to alendronate 10 mg/day orally. OC and PINP were measured in fasting-state serum samples obtained at baseline and at 1, 6, 18, and 36 months. Baseline bone formation markers were below the reference interval (low) in 33% of patients for OC and in 4% of patients for PINP. On teriparatide therapy, the median OC and PINP levels increased by 92% and 108%, respectively, and this resulted in only 12% and 1% of patients being low at 6 months. On alendronate therapy, the median OC and PINP levels decreased by 40% and 53%, respectively, and this resulted in 68% and 34% of patients being low at 6 months. We conclude that bone formation as determined by surrogate markers was increased in teriparatide-treated patients with GIO and decreased in alendronate-treated patients with GIO.

MOUSE SYSTEMS FOR STUDYING THE GENETICS OF HYPERTENSION AND RELATED DISORDERS

The determination of cardiovascular diseases by multiple genetic and environmental factors makes it challenging to study the impact of any one genetic factor as a single variable. This review describes how to combine gene targeting in mice with carefully designed breeding strategies to determine the effect of precisely defined mutations as single variables. Studies of mice having mutations in cardiovascular genes should help to clarify the complex genetic determination of hypertension and related diseases.

Effects of teriparatide on hip and upper limb fractures in patients with osteoporosis: A systematic review and meta-analysis

In randomized clinical trials (RCTs) with teriparatide, the number of patients with incident hip fractures was small and insufficiently powered to show statistically significant differences between groups. We, therefore, conducted a systematic review and meta-analysis of the efficacy of teriparatide in the reduction of hip and upper limb fractures in women and men with osteoporosis. A comprehensive search of databases until 22 November 2017 was conducted for RCTs of at least 6-month duration that reported non-spine fractures (hip, humerus, forearm, wrist), either as an efficacy or safety endpoint. Only RCTs that included patients with the approved treatment indications and dose for use of teriparatide were included; trials with off-label use of teriparatide were excluded. Two independent reviewers performed study selection and data extraction. Statistical procedures included Petos method and Mantel-Haenszel with empirical correction, as most of the RCTs reported zero events in at least one of the treatment arms. Study results are expressed as odds ratios (OR) with 95% confidence intervals (CI). Publication bias and heterogeneity were evaluated with standard statistical tests. Twenty-three RCTs were included, 19 with an active-controlled arm (representing 64.9% of the patients included in the control group) and 11 double-blind, representing data on 8644 subjects, 3893 of them treated with teriparatide. Mean age (SD) was 67.0 (4.5) years, median treatment duration 18 months (range: 6 to 24 months). A total of 34 incident hip, 31 humerus, 31 forearm, and 62 wrist fractures were included. Meta-analysis results showed an OR (95% CI) for hip fractures of 0.44 (0.22-0.87; p = 0.019) in patients treated with teriparatide compared with controls. The effects on the risk of humerus [1.02 (0.50-2.08)], forearm [0.53 (0.26-1.08)] and wrist fractures [1.21 (0.72-2.04)] were not statistically significant (p > 0.05). This meta-analysis provides evidence of efficacy of teriparatide in reducing hip fractures by 56% in patients with osteoporosis.