Cyclic fluctuations in human serum lipid and apolipoprotein levels during the normal menstrual cycle: comparison with changes occurring during oral contraceptive therapy

Lipid metabolism and endometrial receptivity

BACKGROUND

Obesity has now been recognized as a high-risk factor for reproductive health. Although remarkable advancements have been made in ART, a considerable number of infertile obese women still suffer from serial implantation failure, despite the high quality of embryos transferred. Although obesity has long been known to exert various deleterious effects on female fertility, the underlying mechanisms, especially the roles of lipid metabolism in endometrial receptivity, remain largely elusive.

OBJECTIVE AND RATIONALE

This review summarizes current evidence on the impacts of several major lipids and lipid-derived mediators on the embryonic implantation process. Emerging methods for evaluating endometrial receptivity, for example transcriptomic and lipidomic analysis, are also discussed.

SEARCH METHODS

The PubMed and Embase databases were searched using the following keywords: (lipid or fatty acid or prostaglandin or phospholipid or sphingolipid or endocannabinoid or lysophosphatidic acid or cholesterol or progesterone or estrogen or transcriptomic or lipidomic or obesity or dyslipidemia or polycystic ovary syndrome) AND (endometrial receptivity or uterine receptivity or embryo implantation or assisted reproductive technology or in vitro fertilization or embryo transfer). A comprehensive literature search was performed on the roles of lipid-related metabolic pathways in embryo implantation published between January 1970 and March 2022. Only studies with original data and reviews published in English were included in this review. Additional information was obtained from references cited in the articles resulting from the literature search.

OUTCOMES

Recent studies have shown that a fatty acids-related pro-inflammatory response in the embryo-endometrium boundary facilitates pregnancy via mediation of prostaglandin signaling. Phospholipid-derived mediators, for example endocannabinoids, lysophosphatidic acid and sphingosine-1-phosphate, are associated with endometrial receptivity, embryo spacing and decidualization based on evidence from both animal and human studies. Progesterone and estrogen are two cholesterol-derived steroid hormones that synergistically mediate the structural and functional alterations in the uterus ready for blastocyst implantation. Variations in serum cholesterol profiles throughout the menstrual cycle imply a demand for steroidogenesis at the time of window of implantation (WOI). Since 2002, endometrial transcriptomic analysis has been serving as a diagnostic tool for WOI dating. Numerous genes that govern lipid homeostasis have been identified and, based on specific alterations of lipidomic signatures differentially expressed in WOI, lipidomic analysis of endometrial fluid provides a possibility for non-invasive diagnosis of lipids alterations during the WOI.

WIDER IMPLICATIONS

Given that lipid metabolic dysregulation potentially plays a role in infertility, a better understanding of lipid metabolism could have significant clinical implications for the diagnosis and treatment of female reproductive disorders.

Differential Effects of Estradiol and Progesterone on Cardiovascular Risk Factors in Postmenopausal Women

Context

Controlled, blinded studies of sex-hormone replacement in postmenopausal women using natural estradiol (E₂) and native progesterone (P) are few.

Objective

To delineate the effect of E₂ alone or with P on lipids and inflammatory markers.

Design

A placebo-controlled, double-masked, prospectively randomized study of 40 healthy, postmenopausal volunteers assigned to four treatment groups: placebo, intramuscular E₂, and/or micronized oral P for 23 (±2) days.

Results

Treatment with E₂ alone compared with placebo lowered total cholesterol (TC; P = 0.006), non-high-density lipoprotein cholesterol (nonHDL-C; P = 0.004), low-density lipoprotein cholesterol (LDL-C; P = 0.012), and apolipoprotein B (Apo B; P = 0.02) levels, and raised HDL-C levels (P = 0.03 vs the 3 other groups). Conversely, addition of P to E₂ reduced HDL-C levels (P = 0.015). Triglyceride concentrations manifested no effect on E₂ or P. High-sensitivity C-reactive protein (hsCRP) level was highest in women with E₂ and P replacement (P = 0.018 vs placebo). Leptin and IL-6 concentrations did not vary. P treatment decreased adiponectin levels (P = 0.019). Serum E₂ levels correlated linearly with TC, LDL-C, nonHDL-C, Apo B (all negatively), and SHBG (positively) concentrations. P level correlated negatively with TC (P = 0.029), HDL-C (P = 0.002), and adiponectin (P = 0.002) levels.

Conclusion

In this study, there were individual and interactive effects of E₂ and P on key lipids in postmenopausal individuals.

Canned Navy Bean Consumption Reduces Metabolic Risk Factors Associated with Obesity

The high prevalence of obesity and its metabolic co-morbidities require dietitians to promote lifestyle modifications that can be effectively implemented into practice and are feasible for customers to adhere to. The objective of this study was to determine the effect of commercially available ready-to-eat canned navy beans added to the habitual diet on risk factors associated with obesity. Fourteen overweight and obese adults consumed 5 cups of canned navy beans per week for 4 weeks. The study results demonstrated that bean consumption results in reduced waist circumference in females by 2.5 cm and males by 2.1 cm (P < 0.001). The effect of beans on pulse rate, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL) were sex dependent (P < 0.05). In males, pulse rate, TC, and LDL were decreased by 6.5%, 11.5%, and 18%, respectively. In females, pulse rate increased by 9.6%, and TC and LDL were relatively unchanged. There was a trend for a decreased glucose AUC (P = 0.06) in response to a glucose load. This study demonstrates that consuming 5 cups per week of ready-to-eat canned navy beans for 4 weeks reduces metabolic risk factors associated with obesity and therefore can be used as a tool in dietetic practice.

Variations in lipid levels according to menstrual cycle phase: clinical implications

Understanding variations in lipoprotein cholesterol levels throughout the menstrual cycle is important because there may be clinical implications regarding the appropriate timing of measurement and implications on the design and interpretation of studies in women of reproductive age. Our objective was to review the evidence comparing lipoprotein cholesterol levels throughout the menstrual cycle among premenopausal women. Overall, lipoprotein cholesterol levels were observed to vary in response to changing estrogen levels. Taken together, the evidence suggests that total cholesterol and LDL-C tend to be highest during the follicular phase and to decline during the luteal phase, with HDL C highest around ovulation. Based on these findings, the menstrual cycle phase should be taken into account when evaluating lipoprotein cholesterol levels among reproductive-aged women. Measuring cholesterol levels during menses is recommended for consistent comparisons as this phase can be more reliably identified than other phases, although women within National Cholesterol Education Program acceptable ranges, but near the boundaries when tested during menses, should undergo additional tests.

Reference distributions for apolipoproteins AI and B and B/AI ratios: comparison of a large cohort to the world's literature

Limiting the clinical utility of apolipoproteins AI (apo AI) and B (apo B) and the apo B/AI ratios until the last decade has been the lack of satisfactory methods for quantifying serum levels and credible reference materials. Great technological strides have been made in the last few years. The remaining barrier to more relevant and cost-effective use of serum protein data for diagnosis and prognosis has been the availability of widely recognized reliable reference intervals from birth to old age for both males and females. A total of 82 publications reporting reference intervals have been identified that meet most of the same inclusion criteria used in our prior six studies. These have been analyzed statistically and compared to similar studies, i.e., sufficient number, listed subject criteria, method, and reference material, in general terms. Published smaller studies with constrained age ranges, agree on average with our large series of life-long reference intervals that range from less than one year to over 80 years. This study was performed to assess the degree of agreement between smaller reference interval studies to our large population analysis. This meta-analysis provides support and reassurance that many of the smaller reference intervals published previously fall within reasonable limits of out large population.

No effect of menstrual cycle phase on basal very-low-density lipoprotein triglyceride and apolipoprotein B-100 kinetics

Dyslipidemia, manifested by increased plasma triglyceride (TG), increased total and LDL-cholesterol concentrations and decreased HDL-cholesterol concentration, is an important risk factor for cardiovascular disease. Premenopausal women have a less atherogenic plasma lipid profile and a lower risk of cardiovascular disease than men, but this female advantage disappears after menopause. This suggests that female sex steroids affect lipoprotein metabolism. The impact of variations in the availability of ovarian hormones during the menstrual cycle on lipoprotein metabolism is not known. We therefore investigated whether very-low-density lipoprotein (VLDL)-TG and VLDL-apolipoprotein B-100 (apoB-100) kinetics are different during the follicular (FP) and luteal phases (LP) of the menstrual cycle. We studied seven healthy, premenopausal women (age 27 +/- 2 yr, BMI 25 +/- 2 kg/m(2)) once during FP and once during LP. We measured VLDL-TG, VLDL-apoB-100, and plasma free fatty acid (FFA) kinetics by using stable isotope-labeled tracers, VLDL subclass profile by nuclear magnetic resonance spectroscopy, whole body fat oxidation by indirect calorimetry, and the plasma concentrations of lipoprotein lipase (LPL) and hepatic lipase (HL) by ELISA. VLDL-TG and VLDL-apoB-100 concentrations in plasma, VLDL-TG and VLDL-apoB-100 secretion rates and mean residence times, VLDL subclass distribution, FFA concentration and rate of appearance in plasma, whole body substrate oxidation, and LPL and HL concentrations in plasma were not different during the FP and the LP. We conclude that VLDL-TG and VLDL-apoB-100 metabolism is not affected by menstrual cycle phase.

Soy isoflavones improve plasma lipids in normocholesterolemic, premenopausal women

BACKGROUND

Soy consumption is known to reduce plasma total cholesterol and LDL cholesterol in hypercholesterolemic subjects, but the responsible soy components and the effects in normocholesterolemic subjects remain unclear.

OBJECTIVE

The effects of soy isoflavone consumption on plasma total cholesterol, HDL-cholesterol, LDL-cholesterol, triacylglycerol, apolipoprotein A-I, apolipoprotein B, and lipoprotein(a) concentrations and on LDL peak particle diameter were examined in normocholesterolemic, premenopausal women.

DESIGN

Thirteen healthy, normocholesterolemic, free-living, premenopausal female volunteers took part in this randomized, crossover-controlled trial. Each subject acted as her own control. Three soy isoflavone intakes (control: 10.0 +/- 1.1; low: 64.7 +/- 9.4; and high: 128.7 +/- 15.7 mg/d), provided as soy protein isolate, were consumed for 3 menstrual cycles each. Total cholesterol, HDL cholesterol, LDL cholesterol, and triacylglycerol were measured over the menstrual cycle. Apolipoprotein A-I, apolipoprotein B, lipoprotein(a), and LDL peak particle diameter were evaluated in the midluteal phase.

RESULTS

Total cholesterol, HDL-cholesterol, and LDL-cholesterol concentrations changed significantly across menstrual cycle phases (P < 0.005). During specific phases of the cycle, the high-isoflavone diet lowered LDL cholesterol by 7.6-10.0% (P < 0.05), the ratio of total cholesterol to HDL cholesterol by 10.2% (P < 0.005), and the ratio of LDL to HDL cholesterol by 13.8% (P < 0.002).

CONCLUSIONS

Isoflavones significantly improved the lipid profile across the menstrual cycle in normocholesterolemic, premenopausal women. Although of small magnitude, these effects could contribute to a lower risk of developing coronary heart disease in healthy people who consume soy over many years.

Effect of 14 weeks of resistance training on lipid profile and body fat percentage in premenopausal women

OBJECTIVES

To study the effects of a supervised, intensive (85% of one repetition maximum (1-RM)) 14 week resistance training programme on lipid profile and body fat percentage in healthy, sedentary, premenopausal women.

SUBJECTS

Twenty four women (mean (SD) age 27 (7) years) took part in the study. Subjects were randomly assigned to either a non-exercising control group or a resistance exercise training group. The resistance exercise training group took part in supervised 45-50 minute resistance training sessions (85% of 1-RM), three days a week on non-consecutive days for 14 weeks. The control group did not take part in any structured physical activity.

RESULTS

Two way analysis of variance with repeated measures showed significant (p < 0.05) increases in strength (1-RM) in the exercising group. There were significant (p < 0.05) decreases in total cholesterol (mean (SE) 4.68 (0.31) v 4.26 (0.23) mmol/1 (180 (12) v 164 (9) mg/dl)), low density lipoprotein (LDL) cholesterol (2.99 (0.29) v 2.57 (0.21) mmol/l (115 (11) v 99 (8) mg/dl), the total to high density lipoprotein (HDL) cholesterol ratio (4.2 (0.42) v 3.6 (0.42)), and body fat percentage (27.9 (2.09) v 26.5 (2.15)), as well as a strong trend towards a significant decrease in the LDL to HDL cholesterol ratio (p = 0.057) in the resistance exercise training group compared with their baseline values. No differences were seen in triglycerides and HDL cholesterol. No changes were found in any of the measured variables in the control group.

CONCLUSIONS

These findings suggest that resistance training has a favourable effect on lipid profile and body fat percentage in healthy, sedentary, premenopausal women.

Elevated high-density lipoprotein cholesterol and dietary fat intake in women with cyclic mastopathy

OBJECTIVE

This study was designed to examine the contribution of plasma lipids to the pathophysiology of cyclic mastopathy, before and after consideration of diet and sex hormones.

STUDY DESIGN

Thirty-four women with severe cyclic mastopathy (case patients) and 29 women without cyclic mastopathy (control subjects) recorded their breast symptoms daily during 1 menstrual cycle. During each menstrual phase (follicular, early luteal, late luteal, and menstrual) they prospectively completed 2 24-hour dietary diaries, provided blood for lipid and hormone assays, and underwent anthropometric measurements.

RESULTS

Mean age was 34 years. Premenstrual breast swelling and tenderness were significantly more severe in case patients (P < .0001). Cyclic change (late luteal vs follicular) of high-density lipoprotein cholesterol differed between case patients and control subjects, with case patients having a relative excess of high-density lipoprotein cholesterol in the premenstrual phase (P = .01). Dietary fat intake was greater throughout the cycle in case patients (37.5 vs 33.7% of calories, P = .02), and case patients reported increased appetite in the premenstrual phase (P = .01). In multivariate analyses the contributions of mean dietary fat intake and of cyclic change in high-density lipoprotein cholesterol were independently significant, with odds ratios for upper versus lower quintiles being slightly >5.

CONCLUSIONS

Women with cyclic mastopathy had a relative excess of high-density lipoprotein cholesterol during the symptomatic late luteal phase of the menstrual cycle and a higher fat intake throughout the cycle than did control subjects. These observations support the hypothesis that lipids (notably high-density lipoprotein cholesterol) and a high-fat diet play a role in the pathophysiologic characteristics of cyclic mastopathy.

Cyclical variation of plasma lipids, apolipoproteins, and lipoprotein(a) during menstrual cycle of normal women

We report herein the effects of cyclical variations of endogenous sex steroids during the menstrual cycle on plasma lipids and apolipoproteins (apo) in normal women. We examined 16 normal women (age range 25-36 yr) with normal menstrual cycles of 28-31 days. The study covered the period from the 1st day of a menstrual phase (basal) until the 1st day of the following menstrual phase. During the study all women maintained a normolipidic diet (30% fat). Plasma total cholesterol and low-density-lipoprotein cholesterol were significantly higher than basal in the preovulatory phase until progesterone started to increase in the postovulatory phase [day +8 from luteinizing hormone (LH) surge]. High-density-lipoprotein cholesterol was significantly higher than basal from day -1 to the day after LH surge, whereas plasma apoAI levels were significantly higher from day -8 to day +8 (from LH surge). Plasma apo(a) increased significantly during the luteal phase in four women characterized by a single S4 band and lower basal plasma levels of apo(a). Our results indicate that endogenous female sex steroids have significant effects on the circulating levels of plasma lipids and apolipoproteins, including apo(a). More work needs to be done to elucidate the significance of the observed apo(a) changes, and the different phases of the menstrual cycle must be taken into account when evaluating the lipidic risk profile in premenopausal women.

Variations in plasma volume affect total and low-density lipoprotein cholesterol concentrations during the menstrual cycle

Serum lipids are known to vary during the menstrual cycle. To determine if changes in plasma volume contribute to this effect, we determined serum lipids, lipoproteins, and estimated changes in plasma volume in 18 premenopausal women at the start of and at 5-day intervals after menstruation. Eleven men served as a comparison group. Changes in plasma volume were estimated from changes in hemoglobin and hematocrit. Total and low-density lipoprotein (LDL) cholesterol (mean +/- SD) increased 15 +/- 14 mg/dL (9% +/- 10%) and 11 +/- 13 (11% +/- 14%) within 10 days after the start of menstruation (P < .05) and then decreased toward baseline during the rest of the cycle. High-density lipoprotein (HDL) cholesterol increased 3 mg/dL, or 5%, (P < .05) on days 10 and 15 after menstruation. Plasma volume decreased 4% +/- 9% (P < .06) 10 days after the start of menstruation, and this maximum decrease in plasma volume coincided with peak increases in total, LDL, and HDL cholesterol. Except for an 8-mg/dL increase in LDL cholesterol at day 5, lipid changes were no longer significant after adjusting for changes in plasma volume. We conclude that alterations in plasma volume account for approximately half of the increase in total and LDL cholesterol during the menstrual cycle.

Increases in dietary cholesterol are associated with modest increases in both LDL and HDL cholesterol in healthy young women

We studied the effects of dietary cholesterol intake on lipid and lipoprotein levels in healthy young women (n = 13) who were otherwise eating an American Heart Association (AHA) diet. The study used a randomized, three-way crossover design to determine the effects of 0, 1, or 3 eggs added per day (dietary cholesterol range, 108 to 667 mg/d). Each of the three diets was eaten for 8 weeks, with a washout period between diets. Three fasting blood samples were obtained during the last 3 weeks of each diet period to observe changes in fasting plasma lipid levels associated with the menstrual cycle. We also obtained blood just before and 4 and 8 hours after the subjects ingested a standard high-fat formula. During the menstrual cycle, total cholesterol and LDL cholesterol levels fell by 0.051 mmol/L (1.99 mg/dL) and 0.064 mmol/L (2.48 mg/dL) per week, respectively. HDL cholesterol concentrations increased by 0.060 mmol/L (2.3 mg/dL) per week during the first half of the cycle and then fell by 0.050 mmol/L (1.94 mg/dL) per week during the second half. Therefore, all statistical analyses were performed on values adjusted to midcycle. Total fasting cholesterol concentrations increased by 0.073 mmol/L (2.81 mg/dL) per 100 mg dietary cholesterol added to the diet per day (P = .001). LDL cholesterol increased by 0.054 mmol/L (2.08 mg/dL) per 100 mg/d dietary cholesterol (P = .003); this accounted for about 75% of the rise in total cholesterol. HDL cholesterol concentrations increased by 0.015 mmol/L (0.57 mg/dL) per 100 mg/d dietary cholesterol (P < .04). There was a wide range of responses among the women. Plasma apoB levels increased significantly, 0.93 mg/dL per 100 mg/d dietary cholesterol (P = .025), whereas apoA-I levels tended to rise (1.35 mg/dL per 100 mg/d, P = .056). Increases in dietary cholesterol did not produce any observable effects on fasting plasma cholesteryl ester transfer protein levels and had no effect on the response to a standard high-fat formula. Although menstrual-cycle changes in plasma total, LDL, and HDL cholesterol levels were observed, the effects of the diets were similar in the follicular and luteal phases of the menstrual cycle. Additionally, despite changes associated with the menstrual cycle, within-subject variation in plasma total cholesterol was actually smaller in this study than in our study of young men.

Increase of high-density lipoprotein cholesterol at ovulation in healthy women

Plasma cholesterol is believed to vary more in women than in men, with the menstrual cycle, yet our review of the literature found no consistent pattern. We examined variations in plasma lipoproteins in relation to ovarian hormones in 12 healthy, menstruating women. Twenty fasting blood samples were obtained on alternate days over one menstrual cycle; ovulation was timed by hormone measurements. Plasma was analysed enzymatically for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and triacylglycerol (TAG). Low-density lipoprotein cholesterol (LDL-C) was estimated by the Friedewald formula. The greatest effect was seen in HDL-C. Concentrations increased by 12% (P < 0.001) between the times of menstruation and ovulation and remained elevated until the following premenstrual phase. The height of peak oestradiol concentrations at ovulation was significantly associated with HDL-C in that phase (r = +0.75, P < 0.01), and with mean HDL-C concentrations over the whole cycle (r = +0.65, P < 0.05). TC and LDL-C also increased at ovulation, by 9% (P < 0.005) and 11% (P < 0.025) respectively, although the effect was more transient. This study demonstrates that consistent changes in plasma lipoproteins do occur during the menstrual cycle.

The relations between cervical cancer and serological markers of nutritional status

We evaluated whether differences in serological nutrient indicators between cases and controls were likely to be due to different usual levels for cases or to altered metabolism due to disease. Blood samples obtained as part of a case-control study of invasive cervical cancer conducted in Latin America were evaluated for case-control differences and for trends with stage of disease. Serum alpha- and beta-carotene, cryptoxanthin, and alpha- and gamma-tocopherol showed no trend with extent of disease, although Stage IV cases had lower alpha- and beta-carotene values than did other cases. A slight trend of decreasing values with stage was observed for serum retinol, lycopene, and lutein. For cholesterol and triglyceride concentrations, an inverse trend was observed with stage of disease, which suggested a clinical effect of the disease on blood lipids. Adjustment for smoking, alcohol intake, or oral contraceptive use did not alter observed relations, nor was there evidence that the altered blood nutrient levels differed by histological type. These data suggest that serum values for some carotenoids from Stage I, II, and III cervical cancer are suitable for etiological studies, but spurious results may be obtained if late-stage cases are included. Evidence of trends with severity of disease for cholesterol and triglycerides, and possibly for retinol, lycopene, and lutein, suggest that special attention be given to disease effects of these nutrients in studies of cervical cancer.

Variations in the fatty acid composition of lipid classes from lipoproteins in elderly women

Fatty acid composition of lipid classes and NMR spectra of lipoproteins were compared in 6 young (24-35-year-old) and 6 elderly (79-90-year-old) women. Cholesteryl ester, triglyceride and protein content of LDL in elderly women were significantly higher (+52-57% and +20% for lipids and proteins, respectively) than those observed in young women. HDL lipid levels were similar in the two groups. The proportion of linoleic acid (mainly in cholesteryl esters and phospholipids) of each lipoprotein species was always lower in octogenarians when compared with young females (lowering of 13-28% and 27-46% for cholesteryl esters and phospholipids, respectively). Conversely, the proportions of mono-unsaturated fatty acids (mainly oleic acid) increased in all lipid classes, although this was only significant in cholesteryl esters from each lipoprotein species. NMR spectra of lipoproteins showed a restricted mobility of acyl chain terminal CH3 groups in old women which was significant only in VLDL and HDL3. This suggests that the decrease of linoleic acid could affect the lipid mobility in lipoproteins of elderly women.