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Background <p>Salivary immunoglobulin A (IgA) is a key component of oral mucosal immunity, yet its relationships to systemic health are not well defined. We investigated whether salivary IgA relates to systemic immune responses, cardiometabolic risk, and oral microbial diversity and composition.</p> Methods <p>In this cross-sectional study we analyzed adults from the Northern Finland Birth Cohort 1966 at age 46 years. Participants underwent standardized clinical and laboratory assessments and provided saliva and serum samples. The oral microbiome was characterized from salivary samples (<i>n</i> = 863) by 16S rRNA gene sequencing. Salivary IgA and circulating IgA/IgG/IgM were quantified by chemiluminescence immunoassay. Participants were categorized by salivary IgA levels, and immunological, anthropometric, metabolic, inflammatory, and microbiome measures were examined.</p> Results <p>Here we show that higher salivary IgA is associated with greater adiposity, including higher BMI (25.7 vs. 27.2 kg/m²; <i>P</i> = 0.001), percent body fat (27.3% vs. 29.6%; <i>P</i> = 0.031), body fat mass (20.7 vs. 24.0 kg; <i>P</i> = 0.00007), and visceral fat area (95.3 vs. 107.7 cm²; <i>P</i> = 0.002) across salivary IgA quartiles. Salivary IgA is associated with less favorable glycemic profiles: higher fasting glucose (<i>P</i> = 0.018), HbA1c (<i>P</i> = 0.014), and insulin (<i>P</i> = 0.006), and shows a positive association with serum IgA (<i>P</i> = 0.042) while serum IgG, IgM, and high-sensitivity C-reactive protein (hs-CRP) do not differ across salivary IgA quartiles (Kruskal–Wallis, Bonferroni post hoc). Oral microbial α-diversity is lower in the highest IgA quartile compared with the lowest, and specific shifts in the community structure and composition are observed. Oral microbiome α- or β-diversity is not associated with body fat mass.</p> Conclusions <p>In this cross-sectional study, greater adiposity and higher glycemic indices are associated with higher salivary IgA, which in turn is associated with decreased oral microbiome diversity in the absence of overt oral inflammation. These findings are consistent with possible mucosal-metabolic crosstalk and motivate longitudinal and mechanistic studies to determine directionality and clinical implications.</p>

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Mucosal immunoglobulin A mirrors metabolic adiposity and is associated with oral microbiome diversity

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月10日

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  • Miia Hakula,
  • Anton Lavrinienko,
  • Rasmus Hindström,
  • Antti Nissinen,
  • Tuula Salo,
  • Janne J. Koskimäki,
  • Sohvi Hörkkö,
  • Ramin Akhi

摘要

Background

Salivary immunoglobulin A (IgA) is a key component of oral mucosal immunity, yet its relationships to systemic health are not well defined. We investigated whether salivary IgA relates to systemic immune responses, cardiometabolic risk, and oral microbial diversity and composition.

Methods

In this cross-sectional study we analyzed adults from the Northern Finland Birth Cohort 1966 at age 46 years. Participants underwent standardized clinical and laboratory assessments and provided saliva and serum samples. The oral microbiome was characterized from salivary samples (n = 863) by 16S rRNA gene sequencing. Salivary IgA and circulating IgA/IgG/IgM were quantified by chemiluminescence immunoassay. Participants were categorized by salivary IgA levels, and immunological, anthropometric, metabolic, inflammatory, and microbiome measures were examined.

Results

Here we show that higher salivary IgA is associated with greater adiposity, including higher BMI (25.7 vs. 27.2 kg/m²; P = 0.001), percent body fat (27.3% vs. 29.6%; P = 0.031), body fat mass (20.7 vs. 24.0 kg; P = 0.00007), and visceral fat area (95.3 vs. 107.7 cm²; P = 0.002) across salivary IgA quartiles. Salivary IgA is associated with less favorable glycemic profiles: higher fasting glucose (P = 0.018), HbA1c (P = 0.014), and insulin (P = 0.006), and shows a positive association with serum IgA (P = 0.042) while serum IgG, IgM, and high-sensitivity C-reactive protein (hs-CRP) do not differ across salivary IgA quartiles (Kruskal–Wallis, Bonferroni post hoc). Oral microbial α-diversity is lower in the highest IgA quartile compared with the lowest, and specific shifts in the community structure and composition are observed. Oral microbiome α- or β-diversity is not associated with body fat mass.

Conclusions

In this cross-sectional study, greater adiposity and higher glycemic indices are associated with higher salivary IgA, which in turn is associated with decreased oral microbiome diversity in the absence of overt oral inflammation. These findings are consistent with possible mucosal-metabolic crosstalk and motivate longitudinal and mechanistic studies to determine directionality and clinical implications.