Garlic Improves Normal Water and Sodium Handling in Diabetic Kidneys by Attenuating Atrial Natriuretic Peptide: A Comparison with Metformin Treatment

Diabetes mellitus (DM) is a chronic endocrine abnormality characterised by impaired insulin function and systemic hyperglycaemia, which alter fluid balance and hormonal regulation. The cardiac hormone atrial natriuretic peptide (ANP) modulates renal natriuresis and diuresis, and its expression is disrupted in DM. We evaluated the effects of oral aqueous garlic extract (GE) on physiological, biochemical, and molecular parameters in streptozotocin-induced type 1 diabetic male Sprague–Dawley rats, using metformin as a positive control. Parameters assessed included fasting blood glucose (FBG), body weight (BW), fluid intake, urine output, renal sodium excretion, serum ANP concentration, and right atrial ANP and renal NPR-A gene expression via qRT-PCR. GE significantly reduced FBG by 64.8%, attenuated polyuria and polydipsia, and improved BW. GE also downregulated right atrial ANP gene expression by 56.2% and reduced serum ANP concentrations by 34.6%, which occurred alongside a significant reduction in urinary sodium excretion. These findings suggest that GE-induced improvements in fluid and electrolyte balance in type 1 DM are partly mediated through modulation of the ANP signalling pathway.