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Effects of low-calorie and weight-maintenance diets on IgG glycome composition

Obesity-induced inflammation usually starts with the activation of the innate immune system and consequently activates the adaptive immune system which leads to the production of a more inflammatory repertoire of cytokines and pathogenic immunoglobulin G (IgG) antibodies. Each IgG molecule has an N-glycosylation site on each of its heavy chains that influences its structural stability, conformation and half-life, as well as effector functions. For example, a higher proportion of sialic acid and galactose residues is associated with anti-inflammatory activity. IgG glycome has already been well studied and its alterations correlate with different diseases and conditions, including high body mass index (BMI) and central adiposity. Still, this is the first study that studied its susceptibility to different dietary regimes for weight control after the initial weight loss. To explore IgG glycosylation alterations due to weight loss and subsequent weight-maintenance diets, we analyzed 1850 IgG glycomes from subjects of the Diogenes study, one of the largest dietary intervention studies in which subjects underwent a low-calorie diet (LCD) followed by one of five weight-maintenance diets (low protein/low glycaemic index, low protein/high glycaemic index, high protein/low glycaemic index, high protein/high glycaemic index and control) in a period of 6 months when the subjects were vulnerable to regain the weight. The most prominent alteration of the glycome was 8 weeks after the subjects underwent LCD ; a statistically significant decrease of agalactosylated and accompanying increase of sialylated N-glycans in IgG glycome presents shifting from pro- to the anti-inflammatory activity of IgG. These observations were expected knowing that apart from being an energy storage depot, adipose tissue is also an endocrine organ that produces adipokines such as interleukin (IL-6) and tumor necrosis factor-α (TNF-α), cytokines already well-linked with inflammation. Since adipose tissue production is affected by the degree of adiposity, the attenuation of systematic inflammation is an obvious outcome after a reduction diet. Unfortunately, we did not observe significant changes between different diets, and an increased abundance of glycans with bisecting GlcNAc and decreased abundance of sialylated ones, which were present regardless of diet type, suggest a pro- inflammatory direction of IgG glycome alteration in the period of weight-maintaining or regaining.

Effects of low-calorie and weight-maintenance diets on IgG glycome composition

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