Publications by authors named "Karl-Heinz Storbeck"

Objectives: Sex hormone-binding globulin (SHBG) and testosterone are differentially associated with type 2 diabetes (T2D) risk. We investigated whether these associations differ by HIV and menopausal status in Black South African women living with (WLWH) and without HIV (WLWOH).

Design: Cross-sectional observational.

View Article and Find Full Text PDF

Context: 11-oxygenated androgens are a group of adrenal-derived steroids that require peripheral activation. In vitro data highlight a putative role for 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) in 11-oxygenated androgen biosynthesis, converting 11β-hydroxyandrostenedione (11OHA4) to 11-ketoandrostenedione (11KA4), the direct precursor of the potent androgen 11-ketotestosterone (11KT). As the kidney is the major site of HSD11B2 expression, we hypothesized that patients with chronic kidney disease (CKD) would have reduced 11-oxygenated androgen biosynthesis due to impaired HSD11B2 activity.

View Article and Find Full Text PDF

HIV acquisition risk with norethisterone (NET) enanthate (NET-EN) is reportedly less than for depo-medroxyprogesterone acetate intramuscular (DMPA-IM). We investigated the effects of these progestin-only injectable contraceptives on serum testosterone and sex hormone binding globulin (SHBG) levels, since these may play a role in sexual behavior and HIV acquisition. The open-label WHICH clinical trial, conducted at two sites in South Africa from 2018-2019, randomized HIV-negative women aged 18-40 years to 150 mg DMPA-IM 12-weekly (n = 262) or 200 mg NET-EN 8-weekly (n = 259).

View Article and Find Full Text PDF

Chronic psychological stress is a recognized, yet understudied risk factor for heart disease, with potential sex-specific effects. We investigated whether chronic stress triggers sex-dependent cardiac dysfunction in isolated Wistar rat hearts subjected to ischemia-reperfusion injury. The experimental cohort underwent 1 h of daily restraint stress for 4 wk versus matched controls, followed by euthanasia (sodium pentobarbital) and heart excision for ex vivo perfusion.

View Article and Find Full Text PDF

Objectives: To investigate longitudinal changes in SHBG and free testosterone (free T) levels among Black middle-aged African men, with and without coexistent HIV, and explore associations with incident dysglycaemia and measures of glucose metabolism.

Design: This longitudinal study enrolled 407 Black South African middle-aged men, comprising primarily 322 men living without HIV (MLWOH) and 85 men living with HIV (MLWH), with normal fasting glucose at enrollment. Follow-up assessments were conducted after 3.

View Article and Find Full Text PDF

Objective: To explore depot-specific functional aspects of adipose tissue, examining the putative role for menopause and HIV status on insulin sensitivity (SI) and beta-cell function in Black South African women.

Methods: Women (n = 92) from the Middle-Aged Soweto Cohort, including premenopausal HIV-negative women (n = 21); premenopausal women living with HIV (LWH; n = 11); postmenopausal HIV-negative women (n = 42); and postmenopausal women LWH (n = 18) underwent the following tests: body composition (dual-energy x-ray absorptiometry); fasting bloods for sex hormones, inflammation, and adipokines; frequently sampled intravenous glucose tolerance test for SI and beta-cell function (disposition index, DI); abdominal (aSAT) and gluteal subcutaneous adipose tissue (gSAT) biopsies for cell size, and mRNA expression of adipokines, inflammation, and estrogen receptors (ER).

Results: Depot-specific associations between gene expression and insulin parameters did not differ by HIV or menopause status.

View Article and Find Full Text PDF

Epitestosterone is a stereoisomer of the active androgen testosterone and its circulating concentrations are similar to those of testosterone in women and children. However, its biological function and pathways of metabolism remain unknown. The structural similarity to testosterone suggests a potential function in the modulation of androgen receptor signalling.

View Article and Find Full Text PDF

Aldo-keto reductase 1C3 (AKR1C3) is a key enzyme in the activation of both classic and 11-oxygenated androgens. In adipose tissue, AKR1C3 is co-expressed with 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which catalyzes not only the local activation of glucocorticoids but also the inactivation of 11-oxygenated androgens, and thus has the potential to counteract AKR1C3. Using a combination of in vitro assays and in silico modeling we show that HSD11B1 attenuates the biosynthesis of the potent 11-oxygenated androgen, 11-ketotestosterone (11KT), by AKR1C3.

View Article and Find Full Text PDF

Introduction: This study aimed to, first, determine the clusters of sex hormones, liver enzymes, and cardiometabolic factors associated with postprandial glucose (PPG) and, second to evaluate the variation these clusters account for jointly and independently with polygenic risk scores (PRSs) in South Africans of African ancestry men and women.

Research Design And Methods: PPG was calculated as the integrated area under the curve for glucose during the oral glucose tolerance test (OGTT) using the trapezoidal rule in 794 participants from the Middle-aged Soweto Cohort. Principal component analysis was used to cluster sex hormones, liver enzymes, and cardiometabolic factors, stratified by sex.

View Article and Find Full Text PDF

Progestin-only injectable contraceptives, mainly depo-medroxyprogesterone acetate intramuscular (DMPA-IM), are the most widely used contraceptive methods in sub-Saharan Africa. Insufficient robust data on their relative side-effects and serum concentrations limit understanding of reported outcomes in contraception trials. The WHICH clinical trial randomized HIV-negative women to DMPA-IM (n = 262) or norethisterone enanthate (NET-EN) (n = 259) at two South African sites between 2018-2019.

View Article and Find Full Text PDF

Testosterone biosynthesis from its precursor androstenedione is thought to be exclusively catalysed by the 17β-hydroxysteroid dehydrogenases-HSD17B3 in testes, and AKR1C3 in the ovary, adrenal and peripheral tissues. Here we show for the first time that the glucocorticoid activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1) can also catalyse the 17β-reduction of androstenedione to testosterone, using a combination of in vitro enzyme kinetic assays, mathematical modelling, and molecular docking analysis. Furthermore, we show that co-expression of HSD11B1 and AKR1C3 increases testosterone production several-fold compared to the rate observed with AKR1C3 only, and that HSD11B1 is likely to contribute significantly to testosterone production in peripheral tissues.

View Article and Find Full Text PDF
Article Synopsis
  • This study focuses on analyzing the sex steroids testosterone and progesterone in wild giraffes, filling a gap in knowledge about their endocrine profiles in this species.* -
  • Research conducted at Rooipoort Nature Reserve showed that pregnant giraffe females have higher progesterone levels, while male testosterone is linked to age, testicle size, and ossicone volume.* -
  • The findings suggest that hormonal changes in both sexes influence reproductive strategies and maternal care, with male giraffe ossicones playing a role in competitive behavior during mating.*
View Article and Find Full Text PDF

For many decades, the prevailing paradigm in endocrinology was that testosterone and 5α-dihydrotestosterone are the only potent androgens in the context of human physiology. The more recent identification of adrenal derived 11-oxygenated androgens and particularly 11-ketotestosterone have challenged these established norms, prompting a revaluation of the androgen pool, particularly in women. Since being recognized as bone fide androgens in humans, numerous studies have focused their attention on understanding the role of 11-oxygenated androgens in human health and disease and have implicated them as role players in conditions such as castration resistant prostate cancer, congenital adrenal hyperplasia, polycystic ovary syndrome, Cushing's syndrome, and premature adrenarche.

View Article and Find Full Text PDF

Background: Multi-steroid profiling is a powerful analytical tool that simultaneously quantifies steroids from different biosynthetic pathways. Here we present an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) assay for the profiling of 23 steroids using post-column infusion of ammonium fluoride.

Methods: Following liquid-liquid extraction, steroids were chromatographically separated over 5 min using a Phenomenex Luna Omega C column and a water (0.

View Article and Find Full Text PDF

Background: Given the rarity of 11β-hydroxylase deficiency (11βOHD), there is a paucity of data about the differences in clinical and biochemical characteristics of classic (C-11βOHD) and nonclassic 11βOHD (NC-11βOHD).

Objective: To characterize a multicenter pediatric cohort with 11βOHD.

Method: The clinical and biochemical characteristics were retrospectively retrieved.

View Article and Find Full Text PDF

This study demonstrates the application of a mathematical steroidogenic model, constructed with individual in vitro enzyme characterisations, to simulate in vivo steroidogenesis in a diseased state. This modelling approach was applied to the South African Angora goat, that suffers from hypocortisolism caused by altered adrenal function. These animals are extremely vulnerable to cold stress, leading to substantial monetary loss in the mohair industry.

View Article and Find Full Text PDF

Steroid hormones, including glucocorticoids and androgens, exert a wide variety of effects in the body across almost all tissues. The steroid A-ring 5β-reductase (AKR1D1) is expressed in human liver and testes, and three splice variants have been identified (AKR1D1-001, AKR1D1-002, AKR1D1-006). Amongst these, AKR1D1-002 is the best described; it modulates steroid hormone availability and catalyses an important step in bile acid biosynthesis.

View Article and Find Full Text PDF

Objective: Androgens are important modulators of immune cell function. The local generation of active androgens from circulating precursors is an important mediator of androgen action in peripheral target cells or tissues. We aimed to characterize the activation of classic and 11-oxygenated androgens in human peripheral blood mononuclear cells (PBMCs).

View Article and Find Full Text PDF

Androgens are the obligatory precursors of estrogens. In humans, classic androgen biosynthesis yields testosterone, thought to represent the predominant circulating active androgen both in men and women. However, recent work has shown that 11-ketotestosterone, derived from the newly described 11-oxygenated androgen biosynthesis pathway, makes a substantial contribution to the active androgen pool in women.

View Article and Find Full Text PDF

Background: The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) determines prereceptor metabolism and activation of glucocorticoids within peripheral tissues. Its dysregulation has been implicated in a wide array of metabolic diseases, leading to the development of selective 11β-HSD1 inhibitors. We examined the impact of the reversible competitive 11β-HSD1 inhibitor, AZD4017, on the metabolic profile in an overweight female cohort with idiopathic intracranial hypertension (IIH).

View Article and Find Full Text PDF

The roles of androgens in male reproductive development and function in zebrafish are poorly understood. To investigate this topic, we employed CRISPR/Cas9 to generate cyp11c1 (11β-hydroxylase) mutant zebrafish lines. Our study confirms recently published findings from a different cyp11c1-/- mutant zebrafish line, and also reports novel aspects of the phenotype caused by loss of Cyp11c1 function.

View Article and Find Full Text PDF

Testosterone and its 5α-reduced form, 5α-dihydrotestosterone, were previously thought to represent the only active androgens in humans. However, recent studies have shown that the potent androgen, 11-ketotestosterone, derived from the adrenal androgen precursor, 11β-hydroxyandrostenedione, may in fact serve as the primary androgen in healthy women. Yet, despite recent renewed interest in these steroids, their downstream metabolism has remained undetermined.

View Article and Find Full Text PDF

In the last decades in vitro studies highlighted the potential for crosstalk between Hypoxia-Inducible Factor-(HIF) and glucocorticoid-(GC) signalling pathways. However, how this interplay precisely occurs in vivo is still debated. Here, we use zebrafish larvae (Danio rerio) to elucidate how and to what degree hypoxic signalling affects the endogenous glucocorticoid pathway and vice versa, in vivo.

View Article and Find Full Text PDF