The government moved Thursday to strengthen protections against discrimination for women, transgender people, the disabled and others who receive care throughout the health-care system, including those who buy insurance under the Affordable Care Act and providers that receive federal funding. The ACA already bars discrimination based on sex and other factors, but the long-delayed proposed regulation issued Thursday explains how the protections will be applied to insurers and health-care providers, such as hospitals and doctors who receive Medicare and Medicaid payments, and it clarifies the standards federal officials would use in implementing the law. The proposed regulation comes as social attitudes about sexuality and gender are undergoing major shifts.