Are estrogens promoting immune modulation and islet protection in type 1 diabetes?

Single cell regulatory architecture of human pancreatic islets suggests sex differences in β cell function and the pathogenesis of type 2 diabetes

Biological sex affects the pathogenesis of type 2 and type 1 diabetes (T2D, T1D) including the development of β cell failure observed more often in males. The mechanisms that drive sex differences in β cell failure is unknown. Studying sex differences in islet regulation and function represent a unique avenue to understand the sex-specific heterogeneity in β cell failure in diabetes. Here, we examined sex and race differences in human pancreatic islets from up to 52 donors with and without T2D (including 37 donors from the Human Pancreas Analysis Program [HPAP] dataset) using an orthogonal series of experiments including single cell RNA-seq (scRNA-seq), single nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq), dynamic hormone secretion, and bioenergetics. In cultured islets from nondiabetic (ND) donors, in the absence of the in vivo hormonal environment, sex differences in islet cell type gene accessibility and expression predominantly involved sex chromosomes. Of particular interest were sex differences in the X-linked KDM6A and Y-linked KDM5D chromatin remodelers in female and male islet cells respectively. Islets from T2D donors exhibited similar sex differences in differentially expressed genes (DEGs) from sex chromosomes. However, in contrast to islets from ND donors, islets from T2D donors exhibited major sex differences in DEGs from autosomes. Comparing β cells from T2D and ND donors revealed that females had more DEGs from autosomes compared to male β cells. Gene set enrichment analysis of female β cell DEGs showed a suppression of oxidative phosphorylation and electron transport chain pathways, while male β cell had suppressed insulin secretion pathways. Thus, although sex-specific differences in gene accessibility and expression of cultured ND human islets predominantly affect sex chromosome genes, major differences in autosomal gene expression between sexes appear during the transition to T2D and which highlight mitochondrial failure in female β cells.

Lipid metabolism in type 1 diabetes mellitus: Pathogenetic and therapeutic implications

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease with insulin deficiency due to pancreatic β cell destruction. Multiple independent cohort studies revealed specific lipid spectrum alterations prior to islet autoimmunity in T1DM. Except for serving as building blocks for membrane biogenesis, accumulative evidence suggests lipids and their derivatives can also modulate different biological processes in the progression of T1DM, such as inflammation responses, immune attacks, and β cell vulnerability. However, the types of lipids are huge and majority of them have been largely unexplored in T1DM. In this review, based on the lipid classification system, we summarize the clinical evidence on dyslipidemia related to T1DM and elucidate the potential mechanisms by which they participate in regulating inflammation responses, modulating lymphocyte function and influencing β cell susceptibility to apoptosis and dysfunction. This review systematically recapitulates the role and mechanisms of various lipids in T1DM, providing new therapeutic approaches for T1DM from a nutritional perspective.

Prolonged Islet Allograft Function is Associated With Female Sex in Patients After Islet Transplantation

BACKGROUND

Islet transplantation (ITx) has proved to be effective in preventing severe hypoglycemia and improving metabolic control in selected subjects with type 1 diabetes. Long-term graft function remains a challenge. Estrogens have been shown to protect β cells from metabolic stresses and improve revascularization of transplanted human islets in the mouse. We aimed to evaluate the influence of sex in allograft survival of ITx recipients.

METHODS

We analyzed a retrospective cohort of ITx recipients (n = 56) followed-up for up to 20 years. Allograft failure was defined as a stimulated C-peptide <0.3 ng/mL during a mixed-meal tolerance test. Subjects were divided into recipients of at least 1 female donor (group 1) and recipients of male donors only (group 2).

RESULTS

Group 1 subjects (n = 25) were aged 41.5 ± 8.4 years and group 2 subjects (n = 22) 45.9 ± 7.3 years (P = 0.062). Female recipient frequency was 44.8% (n = 13) in group 1 and 55.2% (n = 16) in group 2 (P = 0.145). Group 2 developed graft failure earlier than group 1 (680 [286-1624] vs 1906 [756-3256] days, P = 0.038). We performed additional analyses on female recipients only from each group (group 1, n = 16; group 2, n = 20). Female recipients in group 1 exhibited prolonged allograft function compared with group 2, after adjustment for confounders (odds ratio, 28.6; 95% CI, 1.3-619.1; P < 0.05).

CONCLUSION

Recipients of islets from at least 1 female donor exhibited prolonged graft survival compared with recipients of islets from exclusively male donors. In addition, female recipients exhibited prolonged survival compared with male recipients following ITx of at least 1 female donor.

Sexual dimorphism in the progression of type 2 diabetic kidney disease in T2DN rats

Diabetic kidney disease (DKD) is a common complication of diabetes, which frequently leads to end-stage renal failure and increases cardiovascular disease risk. Hyperglycemia promotes renal pathologies such as glomerulosclerosis, tubular hypertrophy, microalbuminuria, and a decline in glomerular filtration rate. Importantly, recent clinical data have demonstrated distinct sexual dimorphism in the pathogenesis of DKD in people with diabetes, which impacts both severity- and age-related risk factors. This study aimed to define sexual dimorphism and renal function in a nonobese type 2 diabetes model with the spontaneous development of advanced diabetic nephropathy (T2DN rats). T2DN rats at 12- and over 48-wk old were used to define disease progression and kidney injury development. We found impaired glucose tolerance and glomerular hyperfiltration in T2DN rats to compare with nondiabetic Wistar control. The T2DN rat displays a significant sexual dimorphism in insulin resistance, plasma cholesterol, renal and glomerular injury, urinary nephrin shedding, and albumin handling. Our results indicate that both male and female T2DN rats developed nonobese type 2 DKD phenotype, where the females had significant protection from the development of severe forms of DKD. Our findings provide further evidence for the T2DN rat strain's effectiveness for studying the multiple facets of DKD.

Sex Differences in Age-Associated Type 2 Diabetes in Rats-Role of Estrogens and Oxidative Stress

Females live longer than males, and the estrogens are one of the reasons for this difference. We reported some years ago that estrogens are able to protect rats against oxidative stress, by inducing antioxidant genes. Type 2 diabetes is an age-associated disease in which oxidative stress is involved, and moreover, some studies show that the prevalence is higher in men than in women, and therefore there are sex-associated differences. Thus, the aim of this study was to evaluate the role of estrogens in protecting against oxidative stress in type 2 diabetic males and females. For this purpose, we used Goto-Kakizaki rats, which develop type 2 diabetes with age. We found that female diabetic rats showed lower glycaemia levels with age than did diabetic males and that estrogens enhanced insulin sensitivity in diabetic females. Moreover, glucose uptake, measured by positron emission tomography, was higher in the female brain, cerebellum, and heart than in those from male diabetic rats. There were also sex-associated differences in the plasma metabolic profile as determined by metabolomics. The metabolic profile was similar between estrogen-replaced and control diabetic rats and different from ovariectomized diabetic rats. Oxidative stress is involved in these differences. We showed that hepatic mitochondria from females produced less hydrogen peroxide levels and exhibited lower xanthine oxidase activity. We also found that hepatic mitochondrial glutathione oxidation and lipid oxidation levels were lower in diabetic females when compared with diabetic males. Ovariectomy induced oxidative stress, and estrogen replacement therapy prevented it. These findings provide evidence for estrogen beneficial effects in type 2 diabetes and should be considered when prescribing estrogen replacement therapy to menopausal women.

Sex differences underlying pancreatic islet biology and its dysfunction

Background

The sex of an individual affects glucose homeostasis and the pathophysiology, incidence, and prevalence of diabetes as well as the response to therapy.

Scope of the review

This review focuses on clinical and experimental sex differences in islet cell biology and dysfunction during development and in adulthood in human and animal models. We discuss sex differences in β-cell and α-cell function, heterogeneity, and dysfunction. We cover sex differences in communication between gonads and islets and islet-cell immune interactions. Finally, we discuss sex differences in β-cell programming by nutrition and other environmental factors during pregnancy.

Major conclusions

Important sex differences exist in islet cell function and susceptibility to failure. These differences represent sex-related biological factors that can be harnessed for gender-based prevention of and therapy for diabetes.