We previously identified a novel pathway of testosterone action via the androgen receptor (AR) in bone marrow mesenchymal precursor cells (BM-PCs) to negatively regulate fat mass and improve metabolic function in male mice. This was achieved using our PC-AR Gene Replacement mouse model in which the AR is only expressed in BM-PCs and deleted in all other tissues. We hypothesise that the markedly reduced fat mass and increased insulin sensitivity of PC-AR Gene Replacements will confer protection from diet-induced overweight and obesity. To test this, 6-week-old male PC-AR Gene Replacements and controls (WT, global-AR knockouts (KOs)) were fed a chow or high-caloric diet (HCD) for 8 or 18 weeks. Following 8 weeks (short-term) of HCD, WT and Global-ARKOs had markedly increased subcutaneous white adipose tissue (WAT) and retroperitoneal visceral adipose tissue (VAT) mass compared to chow-fed controls. In contrast, PC-AR Gene Replacements were resistant to WAT and VAT accumulation following short-term HCD feeding accompanied by fewer large adipocytes and upregulation of expression of the metabolic genes Acaca and Pnlpa2. Following long-term HCD feeding for 18 weeks, the PC-AR Gene Replacements were no longer resistant to increased WAT and VAT adiposity, however, maintained their improved whole-body insulin sensitivity with an increased rate of glucose disappearance and increased glucose uptake into subcutaneous WAT. In conclusion, the action of testosterone via the AR in BM-PCs to negatively regulate fat mass and improve metabolism confers resistance from short-term diet-induced weight gain and partial protection from long-term diet-induced obesity in male mice.

The Dummerstorf high-fertility mouse line FL1 is a worldwide unique selection experiment for increased female reproductive performance. After more than 190 generations of selection, these mice doubled the amount of offspring per litter compared to the unselected control line. FL1 females have a superior lifetime fecundity and the highest Silver fecundity index that has been described in mice, while their offspring show no signs of growth retardation. The reasons for the increased reproductive performance remained unclear. Thus, this study aims to characterize the Dummerstorf high-fertility mouse line FL1 on endocrine and molecular levels on the female side. We analyzed parameters of the hypothalamic pituitary gonadal axis on both hormonal and transcriptional levels. Gonadotropin-releasing hormone and follicle-stimulating hormone (FSH) concentrations were decreased in FL1 throughout the whole estrous cycle. Luteinizing hormone (LH) was increased in FL1 mice in estrus. Progesterone concentrations were decreased in estrus in FL1 mice and not affected in diestrus. We used a holistic gene expression approach in the ovary to obtain a global picture of how the high-fertility phenotype is achieved. We found several differentially expressed genes in the ovaries of FL1 mice that are associated with different female fertility traits. Our results indicate that ovulation rates in mice can be increased despite decreased FSH levels. Cycle-related alterations of progesterone and LH levels have the potential to improve follicular maturation, and interactions of endocrine and molecular factors lead to enhanced follicular survival, more successful folliculogenesis and therefore higher ovulation rates in female FL1 mice.

Exploration of the dual and opposing facets of estrogen necessitates a clear understanding to diminish the controversy of estrogen regulation in averting the systemic, autoimmune, joint degrading disorder, and rheumatoid arthritis (RA). Experimental evidences consider estrogen as a pivotal enzyme to modulate the disease progression via managing several cellular mechanisms targeting inflammatory markers such as TNF, ILs, nuclear factor kappa B, and other regulatory proteins like matrix metalloproteinases impeding joint erosion and cartilage degradation. Estrogen modulates cellular signaling associated with inflammation, oxidative stress, related cardiovascular risk, and miRNA regulation during RA progression. Studies determining estrogen regulation in RA complicate the resemblance of the outcome as they represent both hyper and hypo level of estrogen is linked to the disease. Although some reports deliver estrogen as malign, there is now increasing evidence of rendering protection dose dependently. Variation in estrogen level causes differential expression of certain proteins and their related signaling which is directly or indirectly linked to RA pathogenesis. This review summarizes the variations in protein expression levels by focusing on the in vitro, in vivo,and clinical studies of estrogen deficiency and treatment. Construction of protein–protein interaction network, GO, and KEGG pathway enrichment analysis of the differentially expressed proteins assist in hypothesizing a potential molecular mechanism of estrogen in RA via in silico studies. Targeting these differential proteins can emerge a new path for developing advanced therapeutic strategies.

Loss-of-function calcium-sensing receptor (CASR) mutations cause mineral metabolism disorders, familial hypocalciuric hypercalcemia, or neonatal severe hyperparathyroidism and increase the risk of femoral fracture, chronic kidney disease, coronary heart disease, and other diseases. In severe cases, CaSR mutations are lethal. Off-label use of the CaSR-positive allosteric modulator (PAM), cinacalcet, corrects hypercalcemia in some patients with CaSR mutations. However, other patients remain unresponsive to cinacalcet, attesting to the need for novel treatments. Here, we compared the effects of cinacalcet to two other clinically approved synthetic CaSR activators, evocalcet and etelcalcetide, as well as a novel PAM, 1-(2,4-dimethylphenyl)-1-(4,5-dimethylthiazol-2-yl)ethan-1-ol (MIPS-VD-836-108) on clinically relevant CaSR mutations. We assessed the compounds in CaSR-expressing HEK293 cells for correction of mutation-induced impairments in intracellular calcium (Ca²⁺ _i) mobilization and cell surface expression. While cinacalcet, MIPS-VD-836-108 and evocalcet rescued the signaling of cell surface-expressed mutants, albeit to varying degrees, etelcalcetide was ineffective. Cinacalcet and evocalcet, but not MIPS-VD-836-108 or etelcalcetide, restored the expression of a R680H mutant. However, no compound rescued expression of I81K and C582R mutants or a receptor missing 77 amino acids in the extracellular domain mimicking deletion of CASRexon 5, which impairs CaSR function. These data suggest specific compounds may be clinically effective in some patients with CaSR mutations, but other patients will remain refractory to treatment with currently available CaSR-targeting activators, highlighting the need for new generation drugs to rescue both the signaling and expression of mutant CaSRs.

There is no common consensus on the physiological role of insulin-like peptide 5 (INSL5) and its cognate receptor, relaxin family peptide receptor 4 (RXFP4). The experimental data for INSL5–RXFP4 expression and function point to a potential role of the peptide hormone and receptor pair in linking energy availability, homeostasis, and inflammation. In this review, we summarize studies on the INSL5–RXFP4 system and propose that the current findings from diverse experimental settings point broadly to a role as a protective energy sensor (PES). Specifically, we review the evidence that (1) INSL5–RXFP4 could regulate immune response by decreasing the production of proinflammatory cytokines and may be involved in the stress response via the HPA axis; (2) INSL5–RXFP4 may signal through sensory neurons on the vagus nerve, transmitting signals to the CNS; and (3) INSL5–RXFP4 could have local autocrine/paracrine roles within the intestinal tract and immune cells. Further investigation and clarification of these proposed roles of INSL5–RXFP4 may prove a greater physiological relevance for the pair and add to existing evidence of INSL5–RXFP4 role as a PES.

Telmisartan and irbesartan are angiotensin II receptor blockers (ARBs) and reportedly stimulate adiponectin secretion from adipocytes via partial peroxisome proliferator-activated receptor γ (PPARγ) activation. However, quantitative evaluation among different ARBs has not been performed. Adiponectin exerts strong protection against a number of pathological events by suppressing cell death, inhibiting inflammation, and enhancing cell survival, while leptin promotes inflammation, oxidative stress, atherogenesis, and thrombosis. The aim of this study was to identify the most effective ARB enhancing adiponectin secretion without raising leptin secretion from human white adipocytes (HWAs). Among seven ARBs (azilsartan, candesartan, irbesartan, losartan, olmesartan, telmisartan, and valsartan), telmisartan was the most effective ARB for the increase of adiponectin secretion and irbesartan was the second, whereas the other ARBs at 1 µM had no effect on adiponectin secretion. GW9662, a PPARγ antagonist, completely blocked pioglitazone (PPARγ agonist)-induced adiponectin secretion and mRNA expression, whereas it unexpectedly blocked neither telmisartan- nor irbesartan-induced adiponectin secretion and mRNA expression but rather increased them. GW6471, PPARα antagonist, and siRNA for PPARα suppressed telmisartan- and irbesartan-induced adiponectin secretion, suggesting that PPARα is the main target of these ARBs to increase adiponectin secretion in HWAs. Leptin secretion was not affected by any ARBs at 1 µM and GW9662 significantly decreased the basal secretion of leptin, suggesting that basal leptin secretion is regulated in a PPARγ-dependent manner. We conclude that telmisartan is the most effective ARB to increase adiponectin secretion via PPARα without raising leptin secretion from HWAs.

Proinsulin C-peptide has a protective effect against diabetic complications; however, its role in hyperglycemia-induced pulmonary fibrosis is unknown. In this study, we investigated the inhibitory effect of C-peptide on hyperglycemia-induced pulmonary fibrosis and the molecular mechanism of C-peptide action in the lungs of diabetic mice and in human pulmonary microvascular endothelial cells (HPMVECs). We found that, in the lungs of diabetic mice, C-peptide supplementation using osmotic pumps attenuated hyperglycemia-induced pulmonary fibrosis and expression of fibrosis-related proteins. In HPMVECs, C-peptide inhibited vascular endothelial growth factor-induced adherens junction disruption and endothelial cell permeability by inhibiting reactive oxygen species generation and transglutaminase (TGase) activation. In the lungs, C-peptide supplementation suppressed hyperglycemia-induced reactive oxygen species generation, TGase activation, and microvascular leakage. C-peptide inhibited hyperglycemia-induced inflammation and apoptosis, which are involved in the pathological process of pulmonary fibrosis. We also demonstrated the role of TGase2 in hyperglycemia-induced vascular leakage, inflammation, apoptosis, and pulmonary fibrosis in the lungs of diabetic TGase2-null (Tgm2^−/− ) mice. Furthermore, we demonstrated a long-term inhibitory effect of systemic delivery of C-peptide using K9-C-peptide hydrogels on hyperglycemia-induced fibrosis in diabetic lungs. Overall, our findings suggest that C-peptide alleviates hyperglycemia-induced pulmonary fibrosis by inhibiting TGase2-mediated microvascular leakage, inflammation, and apoptosis in diabetes.

During bone formation, mesenchymal progenitor cells mature into bone-forming osteoblasts after undergoing several stages of differentiation. Impaired bone formation is a predominant finding in glucocorticoid (GC)-induced osteoporosis (GIO). Osteoblasts at different stages of maturation can be affected by excessive endogenous or therapeutic GCs. Sex-determining region Y-box 2 (SOX2) is normally expressed in immature osteoblasts, but its overexpression can suppress osteoblast differentiation. This study aimed to evaluate whether GC affects SOX2 expression in osteoblasts, and whether SOX2 contributes to GC-induced inhibition of osteoblast differentiation. Treatment with GCs such as dexamethasone (Dex) or hydrocortisone enhanced SOX2 expression. Silencing SOX2 improved inhibition of GC-induced osteoblast differentiation, whereas SOX2 overexpression decreased mineralized nodule formation and RUNX2 and Osterix expression in MC3T3-E1 cells. On the contrary, when C3H10T1/2 uncommitted mesenchymal stem cells were subjected to SOX2 overexpression, RUNX2 expression increased. As a mechanism of Dex-induced SOX2 upregulation in preosteoblasts, we found that the STAT3 pathway or GC receptor (GR) is involved, using a GR antagonist, STAT3 regulators, and chromatin immunoprecipitation assays. Moreover, mice treated with Dex for 4 weeks showed a notable increase in SOX2 expression in the bones and an increased ratio of procollagen type 1 N-terminal propeptide to osteocalcin in the plasma than in control mice. This study demonstrated that GC enhances SOX2 expression in vitro in osteoblast and in vivo in the mice bone, which affects bone-forming activity differently depending on the differentiation stage of osteoblast-lineage cells. Our results provide new insights into prevention and treatment against impaired bone formation in GIO.

Sex hormones play a pivotal role in physiology and disease. Estrogen, the female sex hormone, has been long implicated in having protective roles against obesity. However, the direct impact of estrogens in white adipose tissue (WAT) function and growth is not understood. Here, we show that the deletion of estrogen receptor alpha (ERα; Esr1) from adipocytes using Adipoq-credoes not affect adipose mass in male or female mice under normal or high-fat diet (HFD) conditions. However, loss of ERα in adipocyte precursor cells (APs) via Pdgfra-cre leads to exacerbated obesity upon HFD feeding in both male and female mice, with s.c. adipose (SWAT)-specific expansion in male mice. Further characterization of these mice revealed infertility and increased plasma levels of sex hormones, including estradiol in female mice and androgens in male mice. These findings compromise the study of estrogen signaling within the adipocyte lineage using the Pdgfra-crestrain. However, AP transplant studies demonstrate that the increased AP hyperplasia in male SWAT upon Pdgfra-cre-mediated ablation of ERα is not driven by AP-intrinsic mechanisms but is rather mediated by off-target effects. These data highlight the inherent difficulties in studying models that disrupt the intricate balance of sex hormones. Thus, better approaches are needed to study the cellular and molecular mechanisms of sex hormones in obesity and disease.

Obesity causes white and brown adipocyte dysfunction, reducing browning and stimulating whitening. Drugs that tackle adipocyte dysfunction through thermogenesis stimulation could be used to treat obesity. This study sought to address whether a combination of the PPAR-alpha agonist (WY14643) and DPP4i (linagliptin) potentiates browning and mitigates adipose tissue dysfunction, emphasizing the pathways related to browning induction and the underlying thermogenesis in high-fat-fed mice. Adult male C57BL/6 mice were randomly assigned to receive a control diet (C, 10% lipids) or a high-fat diet (HF, 50% lipids) for 12 weeks. Experiment 1 aimed to evaluate whether 5 weeks of combined therapy was able to potentiate browning using a five-group design: C, HF, HFW (monotherapy with WY14643, 2.5 mg/kg body mass), HFL (monotherapy with linagliptin, 15 mg/kg body mass), and HFC (a combination of both drugs). Experiment 2 further addressed the pathways involved in browning maximization using a four-group study design: C, CC (C diet plus the drug combination), HF, and HFC (HF diet plus the drug combination). The HF group showed overweight, oral glucose intolerance, sWAT adipocyte hypertrophy, and reduced numerical density of nuclei per area of BAT confirming whitening. Only the combined treatment normalized these parameters in addition to body temperature increase, browning induction, and whitening rescue. The high expression of thermogenic marker genes parallel to reduced expression of inflammatory and endoplasmic reticulum stress genes mediated the beneficial findings. Hence, the PPAR-alpha agonist and DPP-4i combination is a promising target for obesity control by inducing functional brown adipocytes, browning of sWAT, and enhanced adaptive thermogenesis.