Normal milk composition in lactating X-linked hypophosphatemic mice despite continued hypophosphatemia

Area of Science:

• Biochemistry
• Genetics
• Physiology

Background:

• X-linked hypophosphatemia (XLH) is characterized by impaired renal phosphate reabsorption and osteomalacia.
• The Hyp gene mutation in mice models XLH, leading to similar phenotypes.
• Altered phosphate transport in organs beyond the kidney remains largely uninvestigated.

Purpose of the Study:

• To investigate phosphate transport in the mammary glands of mice with the Hyp gene mutation.
• To determine if milk composition is altered in heterozygous Hyp mice during lactation.

Main Methods:

• Milk samples were collected from lactating normal and heterozygous Hyp mice 14 days postpartum.
• Analysis included inorganic phosphate, total phosphate, calcium, magnesium, sodium, potassium, cream, fat, water, nonfat organic solids, and protein.
• Litter weight, body weight, and plasma phosphate levels were also measured.

Main Results:

• No significant differences were observed in milk phosphate, calcium, magnesium, potassium, or protein content between normal and Hyp mice.
• Hyp mice milk showed significantly higher sodium content.
• Lactating Hyp mice had lower body weight and plasma phosphate levels compared to lactating normal mice, but milk phosphate accumulation was normal.

Conclusions:

• Despite systemic hypophosphatemia, Hyp mice can maintain normal phosphate levels in their milk.
• These findings suggest that the altered phosphate transport associated with the Hyp gene mutation is primarily localized to the kidney.
• This organ-specific phosphate dysregulation has implications for understanding the broader physiological impact of XLH.