Sterol and lipid metabolism in bees

BACKGROUND

Bees provide essential pollination services for many food crops and are critical in supporting wild plant diversity. However, the dietary landscape of pollen food sources for social and solitary bees has changed because of agricultural intensification and habitat loss. For this reason, understanding the basic nutrient metabolism and meeting the nutritional needs of bees is becoming an urgent requirement for agriculture and conservation. We know that pollen is the principal source of dietary fat and sterols for pollinators, but a precise understanding of what the essential nutrients are and how much is needed is not yet clear. Sterols are key for producing the hormones that control development and may be present in cell membranes, where fatty-acid-containing species are important structural and signalling molecules (phospholipids) or to supply, store and distribute energy (glycerides).

AIM OF THE REVIEW

In this critical review, we examine the current general understanding of sterol and lipid metabolism of social and solitary bees from a variety of literature sources and discuss implications for bee health.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We found that while eusocial bees are resilient to some dietary variation in sterol supply the scope for this is limited. The evidence of both de novo lipogenesis and a dietary need for particular fatty acids (FAs) shows that FA metabolism in insects is analogous to mammals but with distinct features. Bees rely on their dietary intake for essential sterols and lipids in a way that is dependent upon pollen availability.

Classic and 11-oxygenated androgens in serum and saliva across adulthood: a cross-sectional study analyzing the impact of age, body mass index, and diurnal and menstrual cycle variation

OBJECTIVE

11-oxygenated androgens significantly contribute to the circulating androgen pool. Understanding the physiological variation of 11-oxygenated androgens and their determinants is essential for clinical interpretation, for example, in androgen excess conditions. We quantified classic and 11-oxygenated androgens in serum and saliva across the adult age and body mass index (BMI) range, also analyzing diurnal and menstrual cycle-dependent variation.

DESIGN

Cross-sectional. Morning serum samples were collected from 290 healthy volunteers (125 men, 22-95 years; 165 women, 21-91 years). Morning saliva samples were collected by a sub-group (51 women and 32 men). Diurnal saliva profiles were collected by 13 men. Twelve women collected diurnal saliva profiles and morning saliva samples on 7 consecutive days during both follicular and luteal menstrual cycle phases.

METHODS

Serum and salivary steroids were quantified by liquid chromatography-tandem mass spectrometry profiling assays.

RESULTS

Serum classic androgens decreased with age-adjusted BMI, for example, %change kg/m2 for 5α-dihydrotestosterone: men -5.54% (95% confidence interval (CI) -8.10 to -2.98) and women -1.62% (95%CI -3.16 to -0.08). By contrast, 11-oxygenated androgens increased with BMI, for example, %change kg/m2 for 11-ketotestosterone: men 3.05% (95%CI 0.08-6.03) and women 1.68% (95%CI -0.44 to 3.79). Conversely, classic androgens decreased with age in both men and women, while 11-oxygenated androgens did not. Salivary androgens showed a diurnal pattern in men and in the follicular phase in women; in the luteal phase, only 11-oxygenated androgens showed diurnal variation.

CONCLUSIONS

Classic androgens decrease while active 11-oxygenated androgens increase with increasing BMI, pointing toward the importance of adipose tissue mass for the activation of 11-oxygenated androgens. Classic but not 11-oxygenated androgens decline with age.

Diurnal variation in salivary progesterone in fertile Indian women

Research question

Is there a diurnal variation in salivary progesterone levels during menstrual cycle among Indian women?

Design

A longitudinal study was carried out to measure progesterone in saliva among small cross-sectional sample (n = 31) of fertile Indian women of reproductive age comprising young adults (18-25 years, n = 11), adults (26-38 years, n = 9) and middle aged (39-45 years, n = 11). Saliva samples were collected twice daily (morning and evening) across the entire menstrual cycle of 31 women.

Results

Mean ages at enrolment and menarche were 30.6 years and 13.6 years respectively. Fifty-five percent of the women were married. The menstrual cycle range was 20-40 days. After controlling for age and menstrual cycle length, statistically significant diurnal variation in progesterone levels was observed across menstrual cycles with high levels in the morning.

Conclusions

This is the first report on salivary progesterone in subjects with Indian ethnicity and could have clinical implications for designing point of care kits for menstrual cycle management, fertility and reproduction.

Normalizing the Optical Signal Enables Robust Assays with Lateral Flow Biosensors

Lateral flow assays (LFAs) are widely adopted for fast, on-site molecular diagnostics. Obtaining high-precision assay results, however, remains challenging and often requires a dedicated optical setup to control the imaging environment. Here, we describe quick light normalization exam (qLiNE) that transforms ubiquitous smartphones into a robust LFA reader. qLiNE used a reference card, printed with geometric patterns and color standards, for real-time optical calibration: a photo of an LFA test strip was taken along with the card, and the image was processed using a smartphone app to correct shape distortion, illumination brightness, and color imbalances. This approach yielded consistent optical signal, enabling quantitative molecular analyses under different illumination conditions. We adapted qLiNE to detect cortisol, a known stress hormone, in saliva samples at point-of-use settings. The assay was fast (15 min) and sensitive (detection limit, 0.16 ng/mL). The serial qLiNE assay detected diurnal cycles of cortisol levels as well as stress-induced cortisol increase.

Reproducibility of saliva progesterone measured by immunoassay compared to liquid chromatography mass spectrometry

Immunoassay overestimates progesterone in blood, but no studies have tested whether this occurs in saliva. We measured progesterone in saliva using immunoassay and mass spectrometry. We tested the immunoassay for cross reactivity with dehydroepiandrosterone sulfate (DHEA-S) and 17α-hydroxyprogesterone (17α-OHP). Progesterone was significantly higher in immunoassay compared to mass spectrometry. Immunoassay progesterone levels increased in when incremental levels of 17α-OHP standard was added. This effect was not observed with the addition of DHEA-S. Research using salivary progesterone immunoassay techniques should be wary, particularly with individuals taking steroid supplementation or with high levels of progesterone metabolites.

Liquid chromatography-mass spectrometry applications for quantification of endogenous sex hormones

Liquid chromatography, coupled with tandem mass spectrometry, presents a powerful tool for the quantification of the sex steroid hormones 17-β estradiol, progesterone and testosterone from biological matrices. The importance of accurate quantification with these hormones, even at endogenous levels, has evolved with our understanding of the role these regulators play in human development, fertility and disease risk and manifestation. Routine monitoring of these analytes can be accomplished by immunoassay techniques, which face limitations on specificity and sensitivity, or using gas chromatography-mass spectrometry. LC-MS/MS is growing in capability and acceptance for clinically relevant quantification of sex steroid hormones in biological matrices and is able to overcome many of the limitations of immunoassays. Analyte specificity has improved through the use of novel derivatizing agents, and sensitivity has been refined through the use of high-resolution chromatography and mass spectrometric technology. This review highlights these innovations, among others, in LC-MS/MS steroid hormone analysis captured in the literature over the last decade.

Simultaneous quantification of endocannabinoids, oleoylethanolamide and steroid hormones in human plasma and saliva

Endogenous cannabinoids are an increasingly intriguing target for biological research, given the changing legal status of medicinal cannabinoid-based products throughout the world. However, studying the endogenous cannabinoid system is a relatively new field, with few research teams attempting to develop quantitative methods for these important modulatory analytes in human matrices, other than blood. Here we develop and validate simultaneous methods for quantifying arachidonoyl-ethanolamide, 2-arachidonoyl glycerol, oleoylethanolamide, cortisol and progesterone in human plasma and saliva using liquid-liquid extraction combined with ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The method was fully validated over the linear concentration range 1-20 ng/mL for each analyte in plasma (R² = 0.98-0.99) and saliva (R² = 0.99). We find that salivary endogenous cannabinoids and cortisol are acutely responsive to exercise, suggesting that targeting the saliva system may present a convenient way for future research of endogenous cannabinoids. This finding also encourages a broader understanding of the endogenous cannabinoid system during stress responses, and our method may consequently lead to a better understanding of the role of endogenous cannabinoids in peripheral tissues.