Adiposity and metabolic health in Asian populations: an epidemiological study using dual-energy x-ray absorptiometry in Singapore.

BACKGROUND: Type 2 diabetes, cardiovascular disease, and related cardiometabolic disturbances are increasing rapidly in the Asia-Pacific region. We investigated the contribution of excess adiposity, a key determinant of type 2 diabetes and cardiovascular risk, to unfavourable cardiometabolic profiles among Asian ethnic subgroups. METHODS: The Health for Life in Singapore (HELIOS) Study is a population-based cohort comprising multiethnic Asian men and women living in Singapore, aged 30-84 years. We performed a cross-sectional analysis of data from individuals who had assessment of body composition by dual-energy x-ray absorptiometry and metabolic characterisation. In a subset of participants on no medication for type 2 diabetes, hypertension, and hypercholesterolaemia, we tested the relationship of BMI and visceral fat mass index (vFMI) with cardiometabolic phenotypes (glycaemic indices, lipid levels, and blood pressure), disease outcomes (type 2 diabetes, hypercholesterolaemia, and hypertension), and metabolic syndrome score with multivariable regression analyses. FINDINGS: Between April 2, 2018, and Jan 28, 2022, 10 004 individuals consented to be part of the HELIOS cohort, of whom 9067 were included in the study (5404 [59·6%] female, 3663 [40·4%] male; 6224 [68·6%] Chinese, 1169 [12·9%] Malay, 1674 [18·5%] Indian; mean age 52·8 years [SD 11·8]). The prevalence of type 2 diabetes, hypercholesterolaemia, and hypertension was 8·2% (n=744), 27·2% (n=2469), and 18·0% (n=1630), respectively. Malay and Indian participants had 3-4-times higher odds of obesity and type 2 diabetes, and showed adverse metabolic and adiposity profiles, compared with Chinese participants. Excess adiposity was associated with adverse cardiometabolic health indices including type 2 diabetes (p<0·0001). However, while vFMI explained the differences in triglycerides and blood pressure between the Asian ethnic groups, increased vFMI did not explain higher glucose levels, reduced insulin sensitivity, and increased risk of type 2 diabetes among Indian participants. INTERPRETATION: Visceral adiposity is an independent risk factor for metabolic disease in Asian populations, and accounts for a large fraction of type 2 diabetes cases in each of the ethnic groups studied. However, the variation in insulin resistance and type 2 diabetes risk between Asian subgroups is not consistently explained by adiposity, indicating an important role for additional mechanisms underlying the susceptibility to cardiometabolic disease in Asian populations. FUNDING: Nanyang Technological University-the Lee Kong Chian School of Medicine, National Healthcare Group, and National Medical Research Council, Singapore.

Mechanistic basis for potassium efflux-driven activation of the human NLRP1 inflammasome.

Nigericin, an ionophore derived from Streptomyces hygroscopicus, is arguably the most commonly used tool compound to study the NLRP3 inflammasome. Recent findings, however, showed that nigericin also activates the NLRP1 inflammasome in human keratinocytes. In this study, we resolve the mechanistic basis of nigericin-driven NLRP1 inflammasome activation. In multiple nonhematopoietic cell types, nigericin rapidly and specifically inhibits the elongation stage of the ribosome cycle by depleting cytosolic potassium ions. This activates the ribotoxic stress response (RSR) sensor kinase ZAKα, p38, and JNK, as well as the hyperphosphorylation of the NLRP1 linker domain. As a result, nigericin-induced pyroptosis in human keratinocytes is blocked by extracellular potassium supplementation, ZAKα knockout, or pharmacologic inhibitors of ZAKα and p38 kinase activities. By surveying a panel of ionophores, we show that electroneutrality of ion movement is essential to activate ZAKα-driven RSR and a greater extent of K+ depletion is necessary to activate ZAKα-NLRP1 than NLRP3. These findings resolve the mechanism by which nigericin activates NLRP1 in nonhematopoietic cell types and demonstrate an unexpected connection between RSR, perturbations of potassium ion flux, and innate immunity.

Bacteria Display Differential Growth and Adhesion Characteristics on Human Hair Shafts.

Apart from the skin surface, hair represents a significant tissue component with a capacity of bacterial interactions. New information can be obtained about hair function through the characterization of bacterial adherence, colonization, and responses to hair shafts per se. In this proof-of-principle study, we examine the growth kinetics of Gram-positive Staphylococcus aureus and Staphylococcus epidermidis, and Gram-negative Pseudomonas aeruginosa and Escherichia coli in the presence of human hair shafts. We explore the ability of these bacteria to adhere to and colonize hair shaft surfaces, as well as the resulting impact on the hair's surface morphology. We show that hair shafts inhibit the growth of Gram-positive S. aureus and S. epidermidis, while the growth kinetics of P. aeruginosa and E. coli remain unaffected. Scanning electron microscope analysis and steeping studies show that P. aeruginosa and E. coli to adhere to and colonize on human hair shafts without significantly affecting the hair shaft's surface morphology. P. aeruginosa produced a substantial amount of biofilm on the hair shaft surfaces, while E. coli specifically inhabited the edges of the cuticle scales. Taken together, our results demonstrate differences in bacterial responses to human hair shafts, which may provide novel insights into hair and scalp health.

Studies on the Proteome of Human Hair - Identification of Histones and Deamidated Keratins.

Human hair is laminar-fibrous tissue and an evolutionarily old keratinization product of follicle trichocytes. Studies on the hair proteome can give new insights into hair function and lead to the development of novel biomarkers for hair in health and disease. Human hair proteins were extracted by detergent and detergent-free techniques. We adopted a shotgun proteomics approach, which demonstrated a large extractability and variety of hair proteins after detergent extraction. We found an enrichment of keratin, keratin-associated proteins (KAPs), and intermediate filament proteins, which were part of protein networks associated with response to stress, innate immunity, epidermis development, and the hair cycle. Our analysis also revealed a significant deamidation of keratin type I and II, and KAPs. The hair shafts were found to contain several types of histones, which are well known to exert antimicrobial activity. Analysis of the hair proteome, particularly its composition, protein abundances, deamidated hair proteins, and modification sites, may offer a novel approach to explore potential biomarkers of hair health quality, hair diseases, and aging.