Big U.S. companies are paying higher risk premiums when they borrow and finding less demand for their bonds, a sign that investors are worried about rising wages and slowing economic growth hitting corporate profit growth.

Companies are responding by borrowing less: They sold around $8 billion of U.S. investment-grade debt last month, about a seventh of the average for December over the last decade. The low levels of high-grade company borrowing reflect how even if U.S. workers are doing relatively well—a report on Friday said average hourly earnings in December jumped—those wage gains are pressuring companies' bottom lines.

Until Thursday, there had been no corporate bond sales for three weeks. When units of companies like Ford Motor Co. and Duke Energy Corp. broke the drought this week, they received orders equal to about two times the amount of bonds they were selling, far below the average of around three times for corporate debt last year, according to Bloomberg data. The results made some money managers wonder how long the tepid demand would last.