Mexico is among the most negatively affected countries by obesity-related comorbidities. Given the accelerated increase of chronic diseases worldwide, it is essential to take action to address this health problem . In this focused study, the nutritional practices of a specific Mexican population were examined with an intent to elucidate a possible adiponectin association with nutritional and sociodemographic characteristics in young students from the Los Altos, Jalisco region of Mexico. Mexico is a pluricultural nation with diverse mestizo ethnic groups derived from a mixture of indigenous peoples of the Americas, Spanish-Europeans, and to lesser degree, those of African and Asian descent. Accordingly, a wide genetic diversity is found in the different regions of Mexico .
Looking at the region studied here, the Mexican state of Jalisco renders an important contribution to the Mexican economy, contributing approximately 10.8% of the gross domestic product (GDP) primarily through its agricultural and farming sectors. Jalisco’s population is distributed in urban and rural municipalities, the latter of which including the Los Altos region, located primarily in the eastern part of the state of Jalisco . Although approximately 60% of the population of Jalisco is concentrated in the capital city of Guadalajara, according to a 2015 report by the Institute of Statistical and Geographic Information for the state of Jalisco, some 399,724 inhabitants of the state, a relatively significant number, live in Los Altos Jalisco region [41, 42]. Given the Los Altos region is an important religious and cultural center where its inhabitants exhibit varying sociocultural characteristics and are known for preserving older traditions , this population was particularly an attractive research focus given their distinct nutritional and lifestyle practices rendering scientific and medical findings as to this population uniquely important to provide lasting benefits to this and other similarly-situated populations.
With respect to the BMI categories, a considerable amount of malnutrition was discovered (33.5%), distributed across underweight (10.4%), overweight (15.6%), and obesity (7.5%) categories. It should be noted the results of this study contrasted with those reported in the National ENSANUT-2018 Survey with respect to obesity. The ENSANUT-2018 Survey reported obesity in 36.1% of adult subjects (> 20 years old) and in 14.6% of adolescents (12–19 years old), both results some two times greater or more those that found in this study (7.5%) for the young student population. The overweight prevalence was comparable; the underweight prevalence could not be compared as it was not undertaken in the ENSANUT-2018 Survey. The ENSANUT-2016 Survey reported an underweight prevalence of 1.3% in both female and male adults from the central region of Mexico, the same general area where the Los Altos region is located. Interestingly, this study found an overall underweight prevalence of 7.7% with respect to females and 10.4% with respect to females and males combined , some six to ten times greater as those reported in the ENSANUT-2016 Survey. This discrepancy may be due to certain societal influences on women to maintain a specific weight as it relates to body image (auto-perception), particularly given these women living in rural areas may possess fewer opportunities for professional development given they would need to migrate to another city to pursue university studies or a career, and as such, have more available time for self-evaluation in regards to their physical appearance . Furthermore, cultural influences in rural regions of Mexico militate towards women being homemakers and mothers caring for babies and away from women pursuing other activities, perhaps also contributing to this discrepancy. While not a principal focus of this study, the issue of education and professional development of women living in rural areas remains an important topic to be discussed and studied, particularly in Mexico.
A notable difference was found in serum adiponectin levels by gender with women showing higher adiponectin levels in comparison to men (4.3 ± 2.6 µg/mL and 2.3 ± 0.8 µg/mL, respectively, p = 0.001). Indeed, the female gender was identified as a protective factor against hypoadiponectinemia (OR = 0.063, 95% CI 0.013–0.3, p < 0.01). This gender disparity in adiponectin levels has been previously reported by Nishizawa and colleagues (2002). The Nishizawa study demonstrated that plasma adiponectin levels were 35% lower in Japanese adult men (aged 52.6 ± 11.9 years) as compared to Japanese adult women (aged 53.2 ± 12.0 years). No significant differences in serum glucose or insulin levels were found by gender in that study. Additionally, it has been shown that in ICR ovariectomized female mice plasma adiponectin was not altered by the procedure; conversely, elevated levels of plasmatic adiponectin were detected in ICR castrated male mice. That study concluded that the presence of testosterone reduced plasma adiponectin levels, this finding confirmed by a cell culture of 3T3-L1 adipocytes exposed to testosterone with resulting decrease in adiponectin concentration in the culture media. That study also suggested the gender influence on adiponectin may be related to the higher risk of insulin resistance and atherosclerosis in males, as induced by androgens [45–47]. However, the physiological mechanism to explain this inverse relationship between adiponectin [mostly of the higher molecular weight (HMW) adiponectin isoform] and testosterone as between women and men is not yet clear [48, 49]. Interestingly, the study by Leffler and colleagues (2019) shows that altered expression of the estrogen receptor (ERα) in mice leads to interruption of adiponectin signaling, suggesting that adiponectin may have a physiological role association with hormonal ERα . Also noteworthy is the previous research of Andersen (2007) and Böttner (2004) that reported a significant decrease of adiponectin levels associated with increased androgen levels found in boys who were initiating puberty [46, 51]. Hence, several important studies attribute the adiponectin discrepancy between genders as being related to sex hormone influences [46, 52].
Interestingly, in this study, adiponectin levels were positively correlated with HDL-c (Pearson´s r = 0.487, p = 0.01). Increased risk of hypoadiponectinemia was observed in subjects who exhibited low HDL-c levels (OR = 4.92, 95% CI 1.8–13.3, p < 0.01). These findings coincide with previous studies suggesting a positive correlation between adiponectin and the HDL-c lipoprotein. In this context, Wang (2017) investigated the adiponectin role in macrophage reverse cholesterol transport through an in vivo study realized in adiponectin -/- knockout mice treated with intraperitoneal injections of different adiponectin concentrations. After four weeks, serum lipidic profiles were compared to the degree of severity of atherosclerotic lesions of the aorta by histopathological examination, as compared to a control group that received only saline injections (placebo). Interestingly, a significant reduction of the evaluated parameters was shown, including triglycerides, total cholesterol and LDL-c in the test group. Notably, HDL-c levels were significantly increased. In addition, the degree of severity of atherosclerotic damage was reduced in the adiponectin-treated mice as compared to the control group. Also evaluated was the mRNA expression of the ABCA1 gene by real time polymerase chain reaction (RT-PCR) along with the protein levels by Western blot in hepatic tissue. There, the ABCA1 protein and mRNA expression increased significantly in mice treated with adiponectin and the increase was found to be directly proportional to adiponectin concentration. Hence, this suggests that adiponectin plays a key role in the lipoprotein metabolism through the biosynthesis of HDL-c by modulation of the ABCA1 protein [53, 54]. Furthermore, Tsubakio-Yamamoto and colleagues (2012) reported a positive correlation between adiponectin and HDL-c; whereas a negative correlation was observed between adiponectin and specific cholesterol types, particularly the larger sized VLDL molecules and the smaller, dense LDL molecules. Thus, the Tsubakio-Yamamoto study suggested that variance in adiponectin levels may be related to the molecular size of the LDL molecule and the synthesis of HDL molecules (Tsubakio-Yamamoto, 2012). In the present study, a significant difference in HDL-c levels was detected between female and male participants wherein females had higher HDL-c levels than males . It was not possible to discard or confirm a possible interaction between HDL-c and the female gender in regulating adiponectin levels in this study; however, this potential interaction would provide a most interesting opportunity for a follow-up study in the future.
Additionally, this study evaluated dietetic values to determine if a relationship existed between dietary characteristics and adiponectin levels in the target population. Habitual ingestion patterns of the studied population along with corresponding nutrients and caloric intake were compared to national and international guidelines. An adequate energy intake was found in this population overall; whereas, the consumption of fat, proteins and some vitamins including folic acid, vitamin B5 and minerals such as sodium, zinc, phosphorus and selenium, were not consumed in sufficient amounts per RDI standards (data not shown) [38, 56, 57]. The potential association between adiponectin levels and the quantity and quality of nutrients ingested was examined and a positive correlation was discovered as between adiponectin levels and fruit consumption. To a lesser degree, a positive correlation was also discovered between adiponectin levels and vitamin C ingestion. Finally, a negative correlation was discovered between adiponectin levels and sodium consumption pursuant to the ANCOVA multivariate model utilized.
In this respect, Corbi and colleagues (2019) similarly researched changes in adiponectin levels as compared to certain biochemical and anthropometric variables in severely obese persons after a nutritional intervention, including a fiber-rich, hypocaloric diet (1200 Kcal/d), and a four-week physical exercise program was administered. At the conclusion of the intervention, all participants there showed notable reduction in BMI scores and a significant increase in adiponectin levels. Additionally, the effect of genetic variants of the ADIPOQ gene was analyzed (the gene that encodes adiponectin), identifying the most accurate predictor of adiponectin variance as the wild allele for the single nucleotide polymorphism (SNP) c.268G > A in the ADIPOQ gene . The present study does not attribute adiponectin level modulation to a single nutrient given the large variation of diet, food and beverage consumption encountered in the studied population in addition to the lack of a specific intervention being implemented in this study. For these reasons, further research is required to establish a more refined correlation as between adiponectin levels and specific dietary components, such as those found in the traditional Mexican diet. Thus, a future study could incorporate a planned nutritional intervention based on the traditional Mexican diet to reach further conclusions with respect to studying the potential effect of typical Mexican diet on adiponectin levels.