This cross-sectional study was conducted at the GOPD of the LAUTECH, Teaching Hospital, Ogbomoso, Nigeria between August 2013 and July 2014. The study was approved by the Research Ethics Committee of the LAUTECH Teaching Hospital, Ogbomoso, Oyo State, Nigeria.

Every apparently healthy alternate adult attending the GOPD for non-cutaneous complaints were recruited until the sample size of study subjects was completed. The sample size was estimated using the Lwanga and Lewoshow equation and the table for case-control studies [11]. A minimum sample size of 63 participants was required for the cases and the control population. Inclusion criteria for subjects included those consenting and apparently healthy, non-pregnant adults (age >18 year) that fulfilled the NCEP-ATP III criteria for the diagnosis of MetS. We included those adults that fulfill the same conditions, but that did not meet NCEP-ATP III criteria as the control population. We excluded non-consenting adults, those with acute medical or surgical illness, known patients with systemic hypertension, diabetes mellitus, and lipid disorders. Adults presently on anti -lipid agents, steroid cream or tablets, individuals with known Chronic Liver Disease (CLD), Chronic Kidney Diseases (CKD) and Acquired Immunodeficiency Syndrome (HIV/AIDS) were excluded.

Clinical Evaluation: The study participants completed a semi-structured questionnaire on socio-demographic characteristics, self-reported their smoking habit and general wellness status. Clinical questions related to morbidities of obesity such as breathlessness, body aches, and arthralgia of large joints was also documented. Anthropometric characteristics of participants were assessed using standard methods defined in Anthropometry Procedures Manual of the National Health and Nutrition Examination Survey (NHANES) [12]. With the aid of a stadiometer, the height of the participants was measured to the nearest 0.1 cm. Weight was checked using a weighing scale and recorded to nearest 0.1 kg. The waist circumference was taken at the midpoint between the lower margin of the last palpable rib and the top of the iliac crest [13]; the hip circumferenceis taken at the widest portion of the buttocks, with the tape parallel to the floor [13]. All measurement was taken using a stretch-resistant tape measure. Body mass index was calculated using the formula weight/ height2 (kg/m²). The Blood Pressure (BP) readings were obtained from every participant using the A and D UA 767 electronic manometer validated by the British Hypertension Society [14]. For all the measurements, researchers obtained two recordings, and an average was recorded as the study data. A Dermatologist under clear daylight specifically examined for skin disorders associated with the components of MetS. Most dermatological diagnoses were made clinically. Skin biopsy, scrapings, nail clipping for microscopy, culture, and sensitivity were done as necessary to exclude differentials. Flat feet were diagnosed clinically, participants were asked to remove their shoes and stand on a flat surface in full weight bearing position. The feet were examined from the front and back and participants were asked to stand on their toes. The loss of arches that brings the sole to a complete or near-complete contact with the ground indicated the presence of flat feet [15].

Laboratory evaluation: Five milliliters each of fasting venous blood was taken from participants after 8-12 hours overnight fasting for the analysis of Fasting Plasma Glucose (FPG), Total Cholesterol (TC), Triglycerides (TG), High-Density Lipoprotein cholesterol (HDL-c), and Low-Density Lipoprotein cholesterol (LDL-c).

Diagnosis of Metabolic Syndrome: The diagnosis of metabolic syndrome was made using the guideline of the NCEP-ATP III definition of metabolic syndrome. Abdominal obesity is defined by WC ≥102 cm (40 inch) in men and ≥88 cm (35 inch) in women; Serum TG; ≥150 mg/dL (1.7 mmol/L); HDL-C; <40 mg/dL in men (1.03 mmol/L) and < 50 mg/dL (1.29mmol/L) in women; blood pressure: ≥ 130 mmHg systolic or ≥ 85 mmHg diastolic; FPG level of ≥110 mg/dL (6.1 mmol/L). The presence of any three of the above traits in the same individual was recorded as MetS for the study [1].

All categorical variables were analysed using Chi-Square statistics and same represented in fraction and percentages. Fischer exact statistics was utilized as indicated. The continuous variable of interest was analysed using student t-test and results were presented as means and standard deviations. The association between MetS and its components with striae distensae and flat feet was also examined in univariate analysis. To establish an association between MetS, clinical variables and skin diseases, variables that showed significance in univariate analysis were included in the multivariate models. The presence or the absence of MetS and abdominal obesity were set as dependent variables, and the significant predictors in the corresponding univariate analysis were entered into the regression models. The model for MetS was corrected for age and gender while the model for predictors of abdominal obesity was adjusted for type 2 Diabetes Mellitus (DM), age, and gender. All results of interest were presented in tables. Statistics with p<0.05 was taken as significant.

The study recruited 197 consenting adults, of which 65 met the NCEP ATP III criteria for MetS and were included as study subjects while 132 participants that did not meet the NCEP ATP III MetS criteria were included as the control population.

[Table/Fig-1] shows socio-demographic and clinical characteristics of the study participants. The participants were mostly females 139/197 (70.6%) with a mean age of 53.37±17.8 years. No significant age, education and smoking difference existed between MetS subjects and the control population. The MetS population significantly had joint pains (40.0% vs 20.5%, p=0.004), hypertension (67.7% vs 39.4%, p<0.001), diabetes mellitus (53.8% vs. 21.2%, p<0.001), dyslipidemia (93.8% vs. 62.1%, p<0.001) and abdominal obesity (72.3% vs. 31.8%, p<0.001) compared to the controls. Similarly, participants with MetS have significantly lower mean HDL-c (p<0.001) and higher fasting plasma glucose (p<0.001) compared to the controls.

Two hundred and twenty three Skin Diseases (SDs) were noted among 197 participants with a mean occurrence of skin diseases of 1.13. [Table/Fig-2] shows the prevalence of cutaneous disorders in MetS. Of all the documented SDs in MetS subjects, Striae distensae significantly increased the odds of associated MetS by 2.8, (95% confidence intervals: 1.4-5.8, p=0.003) and flat feet increased the same by 2.5, (95% confidence intervals: 1.3-4.9, p=0.005) in univariate analysis. In multivariate analysis, after correction for age and gender, flat feet remained the only significant predictor of underlying MetS, (OR =2.2, 95% confidence intervals: 1.0 – 4.7, p=0.039).

The prevalence and cutaneous correlates of abdominal obesity are as shown in [Table/Fig-3]. Flat feet (42.7%), striae distensae (31.5 %), acrochordon (18.0%), varicose veins (18.0%), erythrasma (12.4%), and Candida intertrigo (12.4%) were the leading dermatoses. Flat feet was significantly associated with abdominal obesity and increased its odds by 5.4 (95% confidence intervals: 2.7-11.1, p<0.001), striae distensae also was significantly associated with central obesity and increased its odds by 3.7, (95% confidence intervals: 1.7– 7.8, p<0.001), candida intertrigo and erythrasma increase same by 15.1, (95% confidence intervals: 2.0– 119.3, p=0.002 respectively) and achrocordon by 3.7, (95% Confidence Interval:1.4- 10.0, p=0.006). The multivariate model for cutaneous correlates of abdominal obesity that corrected for age, gender and type 2 DM did not fit and was not considered further. There was no cutaneous disorder associated with impaired fasting/type 2 DM and dyslipidemia in univariate analysis.

The cohort of participants with Striae distensae and flat feet were evaluated further to find out the peculiarities of the group in relation to the components of MetS. The prevalence of MetS is slightly higher among patients with Striae distensae (52.2% vs. 49.0%) compared to those with flat feet. The patients with Striae distensae and flat feet were both significantly obese (p<0.001) and had higher mean SBP and DBP (p= 0.022, 0.013 vs. 0.034, 0.019 respectively) compared to those without the disorders. Meanwhile, participants with flat feet were more likely to run a wider waist circumference (p<0.001) and had significantly higher mean total cholesterol (p=0.046) and LDL-c (p=0.008) [Table/Fig-4].

The present study showed that flat feet are significant predictor of the presence of MetS after correction for age and gender. In addition, Striae distensae, flat feet, and candida intertrigo are a significant associate of central obesity. We found the prevalence of MetS in the present study to be 65/197 (32.9%) and that of its components: dyslipidemia 143/197(72.6%), abdominal obesity 89 (45.2%), systemic hypertension 96(48.7%), and impaired fasting and diabetes mellitus 63(32.0%).

Flat feet, also known as pes planus is a significant predictor of MetS and a correlate of obesity in the present study. Studies have previously documented flat feet as a physical evidence of overweight and obesity which started from childhood [16]. It has been shown that flat feet resulted from pressure effect of weight gain rather than mere accumulation of fat in the feet. Flat feet in the overweight and obese children were not due to mid-plantar fat pad deposition but prolonged weight bearing effect on the plantar arch [16]. In the present study in addition to obesity and MetS, flat feet are associated with dyslipidemia including higher mean serum total cholesterol and LDL-c. Among children of school age, flat feet was associated with age, weight status, and male gender. Obese children with flat feet are more likely to develop flat feet as adults [17]. A previous study documented a of prevalence of 22.0% among school age children [18], a prevalence which is lower compared to both 38.5%, and 42.7% observed among our participants with MetS and obesity. The presence of flat feet in obese individuals could be an indication for screening for underlying MetS and other cardiovascular risk factors in dark skin population. Other documented disorders related to the pressure effect of obesity include plantar hyperkeratosis, chronic venous insufficiency; lymphedema and adipose dolorosa [18,19]. Disorders such as psoriasis and hidradenitis suppurativa which have been associated with MetS [9], but infrequent in the general tropical population were not documented in association with MetS in this study population.

Striae distensae significantly increased the odds of abdominal obesity by 3.9 when present on the participants’ skin. The fact that pregnant women and those adults on all forms of steroid and other bleaching agents that could cause striae distensae were excluded gave further credence to our findings. Studies have shown that the mass effect of fat accumulation in the body areas prone to such collection is responsible for the stretching of the skin along the cleavage lines perpendicular to the direction of greatest force to produce striae distensae [19,20]. Sudden weight gain is important for the development of striae [19,20]. Striae distensae were mostly observed in the arms, gluteal, and the lateral part of the thighs which are fat accumulation prone regions following increase weight gain. Studies have shown that, the location of striae distensae depends on circumstance surrounding their formation. It will be difficult to completely exclude the impact of past pregnancies in the formation of striae distensae documented in our study among the female participants who had completed their family [21-23]. Some of the women had striae distensae in documented regions where striae gravidarum could be present; such locations include the abdomen, the breast, and thighs [20-23]. However, this might not be the case, because study has shown that prior striae distensae in the same area (abdomen, breast, and thighs) is also a known risk factor for the development of striae during pregnancy [20-23]. The prevalence of striae distensae varies with population studied and the location of the survey [20-26]. In present study, the prevalence of striae distensae (32.3%) in MetS is close to an average of 35.0% documented among non- pregnant women by Al-Himdani S et al., [20]. Apart from the association between MetS and striae distensae as shown in this study, striae distensae have been associated with low serum relaxin level, pelvic relaxation [27], prolapsed [28], and poor quality of life [29].

Obesity as a component of NCEP ATP III MetS is associated with some infectious and non-infectious cutaneous diseases in the present study. flat feet (42.7%), striae (31.5%), varicose veins (18.0%), acrochordon (18.0%), erythrasma (12.4%) and candida intertrigo (12.4%) are the six leading dermatoses. The first three cutaneous disorders could be attributed to the mechanical effect of obesity [20], the high prevalence of erythrasma and candida albican are not unconnected with the sub- tropic weather condition that favour growth of organisms, moisture generation, maceration and inflammation in skin creases [24,25,30]. Boza JC et al., also found striae distensae, pseudoacanthosisnigrican and bacterial infection as significant correlates of obesity [25]. The prevalence of skin diseases associated with MetS documented in our study reflect the dominant effect of obesity on other components of MetS. Baselga TE and Torres PM, opined the prevalence of skin diseases in obesity depends on the time elapsed since diagnosis of obesity and diabetes mellitus [26]. Therefore, the longevity of obesity, the severity of obesity and extent of insulin resistance in the sampled population might be responsible for the variations in the proportion of observed skin diseases noted in different studies [24-26].

Concerning evidence of insulin resistance and the cutaneous proof of dyslipidemia in this study, we did show in similarity to Boza JC et al., that central obesity is associated with acrochordon, however, no such association was shown between acrochordon and type 2 diabetes mellitus in the present study [25]. Wali V and Wali VV, also found a correlation between acrochordon, higher levels of TGC, LDL, Very Low-Density Lipoprotein cholesterol (VLDL), leptin, glucose, and glycated haemoglobin [31]. Pseudo acanthosisnigrican is another known evidence of insulin resistance that is usually found in association with achrocordons [24-26], but had no significant association with central obesity and impaired blood sugar and or type 2 DM in this study. Hyperandrogenism although documented, but was not of statistical significance in their association with impaired blood sugar and DM nor central obesity in this study. The explanations for the difference in findings could include the fact that the present study was based in a general outpatient setting and included cases of mild to moderate obesity with an overall mean BMI of 26.90±6.92 kg/m². The severity of obesity likely influence the prevalence of impaired fasting glucose/type 2 diabetes and dyslipidemia in the present study in difference to studies conducted among diabetes mellitus patients. Impaired fasting glucose/type 2 diabetes and dyslipidemia are seen as consequences of obesity. Therefore, it is not strange, that skin evidences of MetS is predominated by obesity prominently in this study.

The prevalence of MetS in this study is 32.9% (65/197). The prevalence of its components: dyslipidemia 143 (72.6%), abdominal obesity 89 (45.2%), systemic hypertension 96 (48.7%), and impaired fasting and diabetes 63 (32.0%) are higher but comparable to findings of Sabir AA et al., in the North Western Nigeria [32]. As found in this study, dyslipidemia was the prevalent component of MetS while impaired fasting blood sugar was the least common. This finding is in agreement with previous studies that sampled apparently normal population [32,33]. The variations in the prevalence of MetS and its components in studies has been attributed to the criteria for diagnosis of MetS [34]. The finding of dyslipidemia of normal triglyceride relative to low HDL cholesterol among the African descent known as triglyceride paradoxseen in this study and demonstrated by others [35] could suggest the need for a different definition for dyslipidemia among dark skin people. A Study of skin markers of MetS is relatively new but could be a necessary, easy and cheaper preventive tool in predicting underlying MetS from cutaneous perspective.

The study was hospital -based, the sample might not be representative of the population in Ogbomoso, and its broader generalization is therefore limited. The number of cases of metabolic syndrome included in the present study was the minimum required and this has implications on the statistical strength of the study. However, despite these limitations, this kind of study was still relevant in the resource-limited settings.

The presence of flat feet was a significant predictor of underlying MetS. Obesity was associated with striae distensae, candida intertrigo, and flat feet. Skin disorders documented in the present study reflected the dominant role of obesity on other components of MetS, and the pattern found in the darkly pigmented skin is similar to the findings documented elsewhere in the world except in those skin diseases not known to be prevalent in our environment. In addition to obesity and MetS, flat feet are significantly associated with higher mean TC and LDL-C. The presence of flat feet in obese individual could be seen as a window to suggest the presence of MetS and screening for the other cardiovascular risk factors.