Background Hip fracture is a public health concern because of its considerable morbidity, excess mortality, great risk of disability, and high societal healthcare costs. China has the largest population of older people in the world and is experiencing rapid population aging and facing great challenges from an increasing number of hip fractures. However, few studies reported the epidemiology, especially at a national level. We aimed to evaluate trends in hip fracture incidence and associated costs for hospitalization in China. Methods and findings We conducted a population-based study using data between 2012 and 2016 from the national databases of Urban Employee Basic Medical Insurance and Urban Resident Basic Medical Insurance in China, covering about 480 million residents. Data from around 102.56 million participants aged 55 years and older during the study period were analyzed. A total of 190,560 incident hip fracture patients (mean age 77.05 years, standard deviation 8.94; 63.99% female) were identified. Primary outcomes included the age-and sex-specific incidences of hip fracture. Associated annual costs for hospitalization were also calculated. Incidence was described as per 100,000 person-years at risk, and 95% confidence intervals were computed assuming a Poisson distribution. Hip fracture incidence overall in China did not increase during the study period despite rapid population aging. Incidence per 100,000
To investigate roles for bone marrow adipocyte (BMAd) lipolysis in bone homeostasis, we created a BMAd-specific Cre mouse model in which we knocked out adipose triglyceride lipase (ATGL, Pnpla2 gene). BMAd-Pnpla2-/- mice have impaired BMAd lipolysis, and increased size and number of BMAds at baseline. Although energy from BMAd lipid stores is largely dispensable when mice are fed ad libitum, BMAd lipolysis is necessary to maintain myelopoiesis and bone mass under caloric restriction. BMAd-specific Pnpla2 deficiency compounds the effects of caloric restriction on loss of trabecular bone in male mice, likely due to impaired osteoblast expression of collagen genes and reduced osteoid synthesis. RNA sequencing analysis of bone marrow adipose tissue reveals that caloric restriction induces dramatic elevations in extracellular matrix organization and skeletal development genes, and energy from BMAd is required for these adaptations. BMAd-derived energy supply is also required for bone regeneration upon injury, and maintenance of bone mass with cold exposure.
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