Pernicious anaemia as a cause of infertility in twins

Loss of the Vitamin B-12 Transport Protein Tcn2 Results in Maternally Inherited Growth and Developmental Defects in Zebrafish

BACKGROUND

In humans, vitamin B-12 (cobalamin) transport involves 3 paralogous proteins: transcobalamin, haptocorrin, and intrinsic factor. Zebrafish (Danio rerio) express 3 genes that encode proteins homologous to known B-12 carrier proteins: tcn2 (a transcobalamin ortholog) and 2 atypical β-domain-only homologs, tcnba and tcnbb.

OBJECTIVES

Given the orthologous relation between zebrafish Tcn2 and human transcobalamin, we hypothesized that zebrafish carrying null mutations of tcn2 would exhibit phenotypes consistent with vitamin B-12 deficiency.

METHODS

First-generation and second-generation tcn2-/- zebrafish were characterized using phenotypic assessments, metabolic analyses, viability studies, and transcriptomics.

RESULTS

Homozygous tcn2-/- fish produced from a heterozygous cross are viable and fertile but exhibit reduced growth, which persists into adulthood. When first-generation female tcn2-/- fish are bred, their offspring exhibit gross developmental and metabolic defects. These phenotypes are observed in all offspring from a tcn2-/- female regardless of the genotype of the male mating partner, suggesting a maternal effect, and can be rescued with vitamin B-12 supplementation. Transcriptome analyses indicate that offspring from a tcn2-/- female exhibit expression profiles distinct from those of offspring from a tcn2+/+ female, which demonstrate dysregulation of visual perception, fatty acid metabolism, and neurotransmitter signaling pathways.

CONCLUSIONS

Our findings suggest that the deposition of vitamin B-12 in the yolk by tcn2-/- females may be insufficient to support the early development of their offspring. These data present a compelling model to study the effects of vitamin B-12 deficiency on early development, with a particular emphasis on transgenerational effects and gene-environment interactions.

Mice lacking the transcobalamin-vitamin B12 receptor, CD320, suffer from anemia and reproductive deficits when fed vitamin B12-deficient diet

In humans, poor nutrition, malabsorption and variation in cobalamin (vitamin B12) metabolic genes are associated with hematological, neurological and developmental pathologies. Cobalamin is transported from blood into tissues via the transcobalamin (TC) receptor encoded by the CD320 gene. We created mice carrying a targeted deletion of the mouse ortholog, Cd320. Knockout (KO) mice lacking this TC receptor have elevated levels of plasma methylmalonic acid and homocysteine but are otherwise healthy, viable, fertile and not anemic. To challenge the Cd320 KO mice we maintained them on a vitamin B12-deficient diet. After 5 weeks on this diet, reproductive failure develops in Cd320 KO females but not males. In vitro, homozygous Cd320 KO embryos from cobalamin-deficient Cd320 KO dams develop normally to embryonic day (E) 3.5, while in vivo, few uterine decidual implantation sites are observed at E7.5, suggesting that embryos perish around the time of implantation. Dietary restriction of vitamin B12 induces a severe macrocytic anemia in Cd320 KO mice after 10-12 months while control mice on this diet are anemia-free up to 2 years. Despite the severe anemia, cobalamin-deficient KO mice do not exhibit obvious neurological symptoms. Our results with Cd320 KO mice suggest that an alternative mechanism exists for mice to transport cobalamin independent of the Cd320 encoded receptor. Our findings with deficient diet are consistent with historical and epidemiological data suggesting that low vitamin B12 levels in humans are associated with infertility and developmental abnormalities. Our Cd320 KO mouse model is an ideal model system for studying vitamin B12 deficiency.

Dietary folate and reproductive success among women undergoing assisted reproduction

OBJECTIVE

To prospectively evaluate the associations of folate with assisted reproductive technology outcomes within a population in the United States.

METHODS

This analysis included women (n=232) in a prospective cohort study at the Massachusetts General Hospital Fertility Center. Diet was assessed before assisted reproductive technology treatment using a validated food frequency questionnaire. Intermediate and clinical endpoints of assisted reproductive technology were abstracted from medical records. Generalized linear mixed models with random intercepts to account for multiple cycles per woman were used to evaluate the association of folate intake with assisted reproductive technology outcomes adjusting for calorie intake, age, body mass index, race, smoking status, infertility diagnosis, and protocol type.

RESULTS

Among the 232 women (median age 35.2 years, median folate intake 1,778 micrograms/day), higher folate intake was associated with higher rates of implantation, clinical pregnancy, and live birth. The adjusted percentage (95% confidence interval [CI]) of initiated assisted reproductive technology cycles resulting in a live birth for women in increasing quartiles of folate intake were 30% (95% CI 21-42%), 47% (95% CI 35-59%), 42% (95% CI 30-35%) and 56% (95% CI 43-67%) (P for trend=0.01). Live birth rates were 20% (95% CI 8-31%) higher among women in the highest quartile of supplemental folate intake (more than 800 micrograms/day) than among women in the lowest quartile (less than 400 micrograms/day). Higher supplemental folate intake was associated with higher fertilization rates and lower cycle failure rates before embryo transfer (P for trend=0.03 and 0.02).

CONCLUSION

Higher intake of supplemental folate was associated with higher live birth rates after assisted reproductive technology treatment.

LEVEL OF EVIDENCE

: II.

Twin studies in autoimmune disease: genetics, gender and environment

Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. High concordance rates among monozygotic (MZ) twins support genetic factors being predominantly involved, whilst low rates are suggestive of environmental factors. Twin studies have often been utilised in the study of systemic and organ specific autoimmune diseases. As an example, type I diabetes mellitus has been investigated to establish that that disease is largely affected by genetic factors, compared to rheumatoid arthritis or scleroderma, which have a weaker genetic association. However, large twin studies are scarce or virtually non-existent in other autoimmune diseases which have been limited to few sets of twins and individual case reports. In addition to the study of the genetic and environmental contributions to disease, it is likely that twin studies will also provide data in regards to the clinical course of disease, as well as risk for development in related individuals. More importantly, genome-wide association studies have thus far reported genomic variants that only account for a minority of autoimmunity cases, and cannot explain disease discordance in MZ twins. Future research is therefore encouraged not only in the analysis of twins with autoimmune disease, but also in regards to epigenetic factors or rare variants that may be discovered with next-generation sequencing. This review will examine the literature surrounding twin studies in autoimmune disease including discussions of genetics and gender.

Prevalence of low serum cobalamin in infertile couples

A high prevalence of low levels of cobalamin had been found in a survey of multi-ethnic normal individuals in Israel. The purpose of this study was to investigate the incidence of cobalamin deficiency among Israeli couples suffering from infertility. All couples seen at the in vitro fertilization clinic at an urban hospital (Shaare Zedek Medical Center) in Jerusalem for a 6-month period were invited. Mean cobalamin levels were 259.2 pg ml(-1) in males and 275.1 pg ml(-1) in females (normal >200 pg ml(-1)), 35.5% of 172 men and 23.3% of 223 females had cobalamin deficiency (P = 0.01). There were 171 couples with complete demographic questionnaires and cobalamin values for each partner. In 74 couples (43.3%), one partner was cobalamin deficient, with no significant difference between those with unexplained infertility versus those with explained infertility; and in 13 couples, both partners were cobalamin deficient. Thirty-nine per cent of all men with an abnormal semen analysis had cobalamin deficiency, a finding that requires further investigation. This study questions whether higher rates of male infertility in Israel are partially ascribable to cobalamin deficiency. Recommendation for supplementation in both males and females to achieve high-normal levels of cobalamin would be prudent.

IVF outcomes are associated with biomarkers of the homocysteine pathway in monofollicular fluid

BACKGROUND

Maternal hyperhomocysteinemia is detrimental for reproduction, but the effects on embryo quality are unknown. The aim of this study was to investigate whether biomarkers of the homocysteine pathway are associated with in vitro fertilization (IVF) outcome.

METHODS

In a prospective study, we investigated biomarkers of the homocysteine pathway for associations with embryo quality and biochemical pregnancy in women undergoing IVF or intracytoplasmic sperm injection treatment (n = 181). In the treatment cycle, blood and monofollicular fluid samples were collected for determination of folate, cobalamin and total homocysteine (tHcy) concentrations.

RESULTS

Of all the women in the study, 67% used folic acid supplements. In blood, a significant correlation was established between high cobalamin and better embryo quality [standardized adjusted regression coefficient: -0.17, 95% confidence interval (CI): -0.30, -0.01]. In monofollicular fluid of non-supplemented women, high cobalamin correlated with better embryo quality (estimate: -0.87; 95% CI: -1.68, -0.06), whereas high tHcy resulted in poor embryo quality (estimate: 1.01; 95% CI: 0.08, 1.95). However, in monofollicular fluid of supplemented women, high tHcy correlated with better embryo quality (estimate: -0.58; 95% CI: -1.12, -0.04). In the total group, a 2-fold increase of monofollicular fluid folate corresponded with a 3.3 times higher chance (95% CI: 1.09, 9.71) of achieving pregnancy.

CONCLUSIONS

An optimal homocysteine pathway in follicular fluid is associated with a better embryo quality and chance of pregnancy.

Infertility in women with pemphigus vulgaris and other autoimmune diseases

BACKGROUND

Pemphigus vulgaris (PV) is an autoimmune disease. Autoimmune diseases may adversely affect reproductive function and could result in infertility.

OBJECTIVE

Our purpose was to describe nine young women with PV and infertility.

METHODS

A retrospective study was performed. Clinical characteristics, immunopathologic features, treatment, clinical course, and long-term follow-up were determined.

RESULTS

Eight of nine patients were unable to become pregnant. One patient became pregnant during a period of remission. In eight of the nine patients, the cause of infertility was ovarian. Anti-sperm antibodies were present in two of the patients.

CONCLUSION

Some patients with PV may have infertility. No definitive conclusion about the frequency of infertility in these patients or its relation to PV can be drawn. However, these observations indirectly demonstrate that there may be important interactions between the immune and hormonal systems.

Cobalamin binding proteins in human seminal plasma

Transcobalamin (TC) and haptocorrin (HC) are present in normal seminal plasma in substance concentrations ten- to twenty-fold that in blood. The results are given in range and (median). The substance concentration of seminal plasma TC is 3.6-21.9 (8.4) nmol l-1 and of seminal plasma HC 1.4-8.6 (3.0) nmol l-1. Compared to normals the substance concentration of TC is significantly lowered in post-vasectomy seminal plasma 2.2-2.9 (5.3) nmol l-1. The Stokes radius and the isoelectric points of seminal plasma TC are identical to TC in blood.

Transcobalamin II in human seminal plasma

Study of cobalamin-binding proteins revealed seminal plasma to be the most concentrated site of transcobalamin II in man. The next richest normal fluid, blood, has approximately one-tenth its concentration. Normal seminal unsaturated cobalamin-binding capacity averaged 15,030 +/- 7,290 pg/ml, of which 11,550 +/- 6,660 pg/ml was transcobalamin II. Transcobalamin II levels were markedly diminished in subjects lacking seminal vesicles (1520-1660 pg/ml), but not after vasectomy. This suggests that seminal vesicles are the chief source of this protein in semen. R binder concentration was increased in postvasectomy subjects (9,970 +/- 4,900 pg/ml vs. 2,980 +/- 1,370 pg/ml in normals) and varied in other patients. The endogenous cobalamin content of semen was only 88-699 pg/ml, and was carried largely by R binder rather than by transcobalamin II. The function of the unusually large seminal transcobalamin II pool in reproduction is unknown, but seems unlikely to be related solely to cobalamin transport needs, at least within the male reproductive tract itself.

Racial patterns in pernicious anemia. Early age at onset and increased frequency of intrinsic-factor antibody in black women

Pernicious anemia affects primarily elderly northern Europeans, but may affect others more often than previously thought. Therefore, we analyzed the data from 156 documented cases: there were 73 patients of "European" origin, 52 black patients and 31 Latin-American patients. The mean age (+/- 1 S.D.) at presentation among black women, 53 +/- 16 years, was lower than that of all the others (P less than 0.001 in most comparisons), and seven of the 33 black women were less than 40 years old. In addition, 23 of the 24 black women tested had circulating antibody to intrinsic factor. A similar though less striking antibody prevalence (85 per cent) and age pattern (60 +/- 13 years) in Latin-American women did not reach statistical significance. No other group exceeded the usual 55 to 70 per cent prevalence of antibody. These finding suggest a different form of or a different response to the disease in black women and perhaps in Latin-American women.

Pregnancy: Nature's experimental system. Transient manifestation of immunological diseases in the child

Major advances in knowledge of immunological diseases have resulted from observation of transient effects on children borne by women with such diseases. The discoveries that in Graves' disease and myasthenia gravis there are IgG antibodies directed against receptors sites are examples of such developments, while "ikiopathic" thrombocytopenic purpura is now accepted as immunological owing to its behaviour during pregnancy. In some instances observations of transient neonatal forms do not correspond with the disease manifestations in the mother. These discrepancies may be due to surgical removal of an organ vital to the disease process; inactivating damage by the disease to such an organ; presence of a blocking antibody of a molecular type not transferred across the placenta; differing tissue-antigen specificity or differing lymphocyte cooperation based on genetic variation. At present there are unexplained observations of fetal/neonatal effects in relation to diabetes mellitus and systemic lupus erythematosus which suggest that study of immunological parameters might be profitable. Determination of the HLA status of mother/fetus pairs may give rewarding clues. In the elucidation of the diseases now proven as antibody-mediated in the antibodies first discovered often turned out to be irrelevant red herrings.